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About The BMJ

Article types and preparation

At The BMJ , we offer authors the opportunity to submit a range of article types. You can find out more about preparing and submitting a particular style of article by clicking on the links below. Please take the time to explore these instructions before proceeding with a submission. Further details about each of these individual sections and article types are discussed further down this page.

Article Types at The BMJ

Requirements for all manuscripts.

Please ensure that anything you submit to The BMJ conforms to the International Committee of Medical Journal Editors’ Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly work in Medical Journals  uniform recommendations for manuscripts submitted to biomedical journals.

Before submitting an article, please ensure that you have followed all guidelines below. We recommend learning about our house style and ways to incorporate images into your submission .

Title page and authorship

The title should be informative and, for research papers, a subtitle with the study design (for example, "a phase III clinical trial" or "a systematic review and meta-analysis").

In this page, please provide for each author his or her name, affiliation (job title) at the time the paper was written, email and, for the corresponding author, the best contact address. All authors must fulfill the ICMJE criteria for authorship . If the number of authors is very large we may ask for confirmation that everyone listed met the ICMJE criteria for authorship . We also offer the option of joint first authorship when two authors meet criteria for such a designation. We reserve the right to require that authors form a group whose name will appear in the article byline. MEDLINE guidance explains that group authorship is acceptable, stating "When a group name for a specific consortium, committee, study group, or the like appears in an article byline, the personal names of the members of that group may be published in the article text. Such names are entered as collaborator names for the MEDLINE citation."

Further details about The BMJ 's stance on authorship, contributorship, and group authorship can be found on our Authorship and contributorship page.

Please note that from 30 November 2018 The BMJ is mandating ORCiD iDs for corresponding authors for all research articles if accepted, and this information will be required alongside submitted manuscripts. Co-authors and reviewers are strongly encouraged to also connect their ScholarOne accounts to ORCiD. We firmly believe that the increased use and integration of ORCiD iDs will be beneficial for the whole research community. For those who do not currently have an iD they will be required to register but this is free and takes a matter of seconds - we strongly encourage all authors to register for an ORCiD profile .

To learn more about ORCiD, please visit http://orcid.org/content/initiative

Contributor and guarantor information

Each contributorship statement should make clear who has contributed what to the planning, conduct, and reporting of the work described in the article, and should identify one, or occasionally more, contributor(s) as being responsible for the overall content as guarantor(s). The guarantor accepts full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish. The following line should also be included - "The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted."

For articles in The BMJ that do not report original research - such as editorials, clinical reviews, and education and debate - please state who had the idea for the article, who performed the literature search, who wrote the article, and who is the guarantor (the contributor who accepts full responsibility for the finished article, had access to any data, and controlled the decision to publish). For non-research articles that include case reports such as lessons of the week, drug points, and interactive case reports, please also state who identified and/or managed the case(s). We encourage authors to fully acknowledge the contribution of patients and the public to their research where appropriate.

Copyright/license for publication

Since January 2000, The BMJ has not asked authors of journal articles to assign us their copyright and authors (or their employers) retain their copyright in the article. All we require from authors is an exclusive licence (or, from government employees who cannot grant this, a non-exclusive licence) that allows us to publish the article in The BMJ (including any derivative products) and any other BMJ products (such as the Student BMJ or overseas editions), and allows us to sublicense such rights and exploit all subsidiary rights.

We ask the corresponding author to grant this exclusive licence (or non-exclusive for government employees) on behalf of all authors by reading our licence and inserting in the manuscript on submission the following statement:

“The Corresponding Author has the right to grant on behalf of all authors and does grant on behalf of all authors, a worldwide licence to the Publishers and its licensees in perpetuity, in all forms, formats and media (whether known now or created in the future), to i) publish, reproduce, distribute, display and store the Contribution, ii) translate the Contribution into other languages, create adaptations, reprints, include within collections and create summaries, extracts and/or, abstracts of the Contribution, iii) create any other derivative work(s) based on the Contribution, iv) to exploit all subsidiary rights in the Contribution, v) the inclusion of electronic links from the Contribution to third party material where-ever it may be located; and, vi) licence any third party to do any or all of the above."

This licence allows authors to use their own articles for their own non-commercial purposes without seeking permission from us. Only if the use is commercial do we need to know about it. In addition, we will pay authors a royalty on certain commercial uses that we negotiate.

Information on permissions for authors and third parties for reuse can be found here .

Manuscripts authored or co-authored by one or more NIH employees must be submitted with a completed and signed NIH Publishing Agreement and Manuscript Cover Sheet according to NIH’s Employee Procedures .

Patient consent (if applicable)

Publication of any personal information about a patient in The BMJ - for example, in a case report or clinical photograph - will normally require the signed consent of the patient. If this is the case, please include a statement that any identifiable patients have provided their signed consent to publication and submit, as a supplemental file, The BMJ 's patient consent form that is available in several languages .

Competing interests declaration

A competing interest - often called a conflict of interest - exists when professional judgment concerning a primary interest (such as patients' welfare or the validity of research) may be influenced by a secondary interest (such as financial gain, academic promotion, or personal rivalry). It may arise for the authors of an article in The BMJ when they have a financial interest that may influence, probably without their knowing, their interpretation of their results or those of others.

We believe that, to make the best decision on how to deal with an article, we should know about any competing interests that authors may have, and that if we publish the article readers should know about them too. We are not aiming to eradicate such interests across all article types in The BMJ . However, certain articles (see below) fall under a stricter policy announced in 2014 . This means that authors whose financial conflicts of interest are judged to be relevant by the BMJ team are not permitted to write these articles. We also ask our staff and reviewers to declare any competing interests.

A declaration of interests for all authors must be received before an article can be reviewed and accepted for publication. It should take one of two forms, depending on what type of article you are submitting. The links to the relevant forms are provided at the end of this section.

For editorials and education articles (excluding State Of The Art reviews and Therapeutics articles)

Since 2014, The BMJ requires that such articles must be written by authors without relevant financial ties to industry . By "industry" we mean companies producing drugs, medical foods, nutraceuticals, devices, apps or tests; medical education companies; or other companies with a financial or reputational interest in the topic of the article. We consider the following relationships with industry to be relevant, making it unlikely that we would be able to publish your work: employment; ownership of stocks and shares (this excludes mutual funds or other situations in which the person is not in a position to control investment decisions) ; travel and accommodation expenses; paid consultancy or directorship; patent ownership; aid membership of speakers' panels or bureaus and advisory board; acting as an expert witness ; being in receipt of a fellowship, equipment, writing, or administrative support; writing or consulting for a medical education promotional or communications company. If you are in doubt about the relevance of any potential conflict of interest please discuss with the editor of the appropriate section before submission.

All authors must review the updated COI policy and complete The BMJ 's Education Declaration of Interests form . If the article is accepted for publication these completed forms will be stored and made available on request. The corresponding author should insert within their manuscript a summary statement derived from the information provided in the COI forms (link below): " I/We have read and understood BMJ policy on declaration of interests and declare the following interests: [list them or state that you have none]."

Examples of different sorts of summary statements:

No competing interests : "We have read and understood BMJ policy on declaration of interests and declare that we have no competing interests."

Competing interests disclosed: " We have read and understood BMJ policy on declaration of interests and declare the following interests: AA is an unpaid member of XX group developing guidelines for ZZ."

For Research and RMR papers

We ask authors of research papers to use a revised version of the ICMJE’s unified disclosure form . The unified form can be used for several journals. Each journal, will, however, integrate the form into its processes in different ways.

Authors must disclose three types of information:

Associations with commercial entities that provided support for the work reported in the submitted manuscript (the timeframe for disclosure in this section of the form is the lifespan of the work being reported).

Associations with commercial entities that could be viewed as having an interest in the general area of the submitted manuscript (in the three years before submission of the manuscript).

Non-financial associations that may be relevant or seen as relevant to the submitted manuscript.

All authors must complete the disclosure form and send it to the corresponding author who will use the information in the forms to craft the COI statement for the paper (examples provided below). The statement but not the forms must be included with the submission. and that must be included with the initial submission. If the paper is accepted, these forms will be required and will be published alongside the article.

The statement in the manuscript should take the following format:

"Competing interests: All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/ and declare: no support from any organisation for the submitted work [or describe if any]; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years [or describe if any]; no other relationships or activities that could appear to have influenced the submitted work [or describe if any].”

Examples of statements:

No competing interests: "All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/ and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work."

Grant funding for research but no other competing interest: "All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/ and declare: all authors had financial support from ABC Company for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work."

Mixed competing interests: "All authors have completed the ICMJE uniform disclosure form at http://www.icmje.org/disclosure-of-interest/ and declare: no support from any organisation for the submitted work; AB has received research grants and honorariums from XYZ company, BF has been paid for developing and delivering educational presentations for BBB foundation, DF does consultancy for HHH and VVV companies; no other relationships or activities that could appear to have influenced the submitted work."

For all other papers

Complete The BMJ 's Disclosure form . We do not need to receive signed copies of the statements regarding competing interests or the licence to publication: these are for information only. When submitting your article (or a revised version of it) you will be prompted at our online editorial office to tick two boxes , confirming that you have read and complied with our policies on competing interests and licence to publication. Please also ensure that your manuscript, whether in original or revised form, also includes your written statements of competing interests and licence to publication.

Additional requirements by Article Type

In addition to the above, all of our articles have additional requirements which should be fulfilled before submitting. For more information on any of the requirements below, please contact [email protected] .

We have produced a checklist to help authors decide whether The BMJ is the right journal for their research. If the work does not seem to fit in The BMJ , it may be better sent straight to another journal with a more specialist or local readership or a higher acceptance rate.

To learn more about the kind of research articles we give priority to, and what services we offer to authors of research, please read the editorial "Publishing your research study in the BMJ ?" . Please note that we welcome studies - even with "negative" results - as long as their research questions are important, new, and relevant to general readers and their designs are appropriate and robust.

Word count and style

To encourage full and transparent reporting of research we do not set fixed word count limits for research articles. Nonetheless, we ask you to make your article concise and make every word count. You will be prompted to provide the word count for the main text (excluding the abstract, references, tables, boxes, or figures) when you submit your manuscript.

Original research articles should follow the IMRaD style (introduction, methods, results, and discussion) and should include a structured abstract (see below), a structured discussion, and a succinct introduction that focuses - in no more than three paragraphs - on the background to the research question.

For an intervention study, the manuscript should include enough information about the intervention(s) and comparator(s) (even if this was usual care) for reviewers and readers to understand fully what happened in the study. To enable readers to replicate your work or implement the interventions in their own practice, please also provide any relevant detailed descriptions and materials (uploaded as one or more supplemental files, including video and audio files where appropriate). Alternatively, please provide in the manuscript URLs to openly accessible websites where these materials can be found.

Please ensure that the discussion section of your article comprises no more than a page and a half and follows this overall structure, although you do not need to signpost these elements with subheadings:

• Statement of principal findings • Strengths and weaknesses of the study • Strengths and weaknesses in relation to other studies, discussing important differences in results • Meaning of the study: possible explanations and implications for clinicians and policymakers • Unanswered questions and future research

This video gives more detailed advice on writing each section of a research paper for The BMJ .

Structured abstract

Please ensure that the structured abstract is as complete, accurate, and clear as possible and has been approved by all authors. We may screen original research articles by reading only the abstract.

Abstracts should be 250- 300 words long: you may need up to 400 words, however, for a CONSORT or PRISMA style abstract. MEDLINE can now handle up to 600 words. Abstracts should include the following headings, but they may be modified for abstracts of clinical trials or systematic reviews and meta-analyses according to the requirements on the the CONSORT extension for abstracts and the PRISMA extension for abstracts , respectively.

• Objectives - a clear statement of the main aim of the study and the major hypothesis tested or research question posed • Design - including factors such as prospective, randomisation, blinding, placebo control, case control, crossover, criterion standards for diagnostic tests, etc. • Setting - include the level of care, eg primary, secondary; number of participating centres. Be general rather than give the name of the specific centre, but give the geographical location if this is important • Participants (instead of patients or subjects) - numbers entering and completing the study, sex, and ethnic group if appropriate. Give clear definitions of how selected, entry and exclusion criteria. • Interventions - what, how, when and for how long. This heading can be deleted if there were no interventions but should normally be included for randomised controlled trials, crossover trials, and before and after studies. • Main outcome measures - those planned in the protocol, those finally measured (if different, explain why). • Results - main results with (for quantitative studies) 95% confidence intervals and, where appropriate, the exact level of statistical significance and the number need to treat/harm. Whenever possible, state absolute rather than relative risks. • Conclusions - primary conclusions and their implications, suggesting areas for further research if appropriate. Do not go beyond the data in the article. Conclusions are important because this is often the only part that readers look at. • Trial registration - registry and number (for clinical trials and, if available, for observational studies and systematic reviews).

When writing your abstract, use the active voice but avoid "we did" or "we found". Numbers over 10 do not need spelling out at the start of sentences. p-values should always be accompanied by supporting data, and denominators should be given for percentages. Confidence intervals should be written in the format (15 to 27) within parentheses, using the word "to" rather than a hyphen. Abstracts do not need references.

Statistical issues

We want your piece to be easy to read but also as scientifically accurate as possible. We encourage authors to review the "Statistical Analyses and Methods in the Published Literature or The SAMPL Guidelines" while preparing their manuscript.

Whenever possible, state absolute rather than relative risks. Please include in the results section of your structured abstract (and in the article's results section) the following terms, as appropriate:

For a clinical trial:

• Absolute event rates among experimental and control groups. • RRR (relative risk reduction). • NNT or NNH (number needed to treat or harm) and its 95% confidence interval (or, if the trial is of a public health intervention, number helped per 1000 or 100,000).

For a cohort study:

• Absolute event rates over time (eg 10 years) among exposed and non-exposed groups • RRR (relative risk reduction)

For a case control study:

• OR (odds ratio) for strength of association between exposure and outcome

For a study of a diagnostic test:

• Sensitivity and specificity • PPV and NPV (positive and negative predictive values)

The box stating 'what is known' and 'what this study adds' should also reflect accurately the above information. Under what this study adds, please give the one most useful summary statistic eg NNT.

Please do not use the term 'negative' to describe studies that have not found statistically significant differences, perhaps because they were too small. There will always be some uncertainty, and we hope you will be as explicit as possible in reporting what you have found in your study. Using wording such as "our results are compatible with a decrease of this much or an increase of this much" or 'this study found no effect' is more accurate and helpful to readers than "there was no effect/no difference." Please use such wording throughout the article, including the structured abstract and the box stating what the paper adds.

Provide one or more references for the statistical package(s) used to analyse the data - for example, RevMan for a systematic review. There is no need to provide a formal reference for a very widely used package that will be familiar to general readers - for example, Stata - but please say in the text which version you used.

Reporting guidelines

Reporting guidelines promote clear reporting of methods and results to allow critical appraisal of the manuscript. We ask that all manuscripts be written in accordance with the appropriate reporting guideline. Please submit as supplemental material the appropriate reporting guideline checklist showing on which page of your manuscript each checklist item appears. A complete list of guidelines can be found in the website of the Equator Network . Below is the list of most often used checklists but others may apply.

For a clinical trials , use the CONSORT checklist and also include a structured abstract that follows the CONSORT extension for abstract checklist, the CONSORT flowchart and, where applicable, the appropriate CONSORT extension statements (for example, for cluster RCTs, pragmatic trials, etc.). A completed TIDieR checklist is also helpful as this helps to ensure that trial interventions are fully described in ways that are reproducible, usable by other clinicians, and clear enough for systematic reviewers and guideline writers.

For systematic reviews or meta-analysis of randomised trials and other evaluation studies, use the PRISMA checklist and flowchart and use the PRISMA structured abstract checklist when writing the structured abstract.

For studies of diagnostic accuracy , use the STARD checklist and flowchart.

For observational studies , use the STROBE checklist and any appropriate extension STROBE extensions.

For genetic risk prediction studies, use GRIPS .

For economic evaluation studies , use CHEERS .

For studies developing, validating or updating a prediction model , use TRIPOD .

For articles that include explicit statements of the quality of evidence and strength of recommendations, we prefer reporting using the GRADE system.

For studies using data from electronic health records, please use CODE-EHR .

Cover letter

A cover letter is your opportunity to introduce your study to the editor, highlighting the most important findings and novelty. Please also include in the letter the following information:

Mandatory patient and public involvement reporting

The BMJ is encouraging active patient and public involvement in clinical research as part of its patient partnership strategy . This is research which is "co produced" with patients, carers, or members of the public. Patient involvement in this context is not about being a research participant, answering surveys, or being an interviewee. It encompasses setting research priorities, defining research questions and outcome measures, providing input into study design and conduct, dissemination of results, and evaluation.

To support co production of research we request that authors provide a short paragraph as a subsection within the methods section of their papers entitled Patient and Public Involvement detailing how they involved the patients and the public in their research. We request this to both encourage the movement and ensure that BMJ readers can easily see whether, and if so how, patients and the public were involved in the research. If they were not involved in any way this information should be formally documented in the Patient and Public Involvement section.

As co production of research with patients and the public is relatively new we appreciate that not all authors will have involved them in their studies. We also appreciate that patient / public involvement may not be feasible or appropriate for all papers. We therefore continue to consider papers where they were not involved.

The Patient and Public Involvement section should provide a brief response to the following questions, tailored as appropriate for the study design reported:

• At what stage in the research process were patients/public first involved in the research and how? • How were the research question(s) and outcome measures developed and informed by their priorities, experience, and preferences? • How were patients/public involved in the design of this study? • How were they involved in the recruitment to and conduct of the study? • Were they asked to assess the burden of the intervention and time required to participate in the research? • How were (or will) patients and the public be involved in choosing the methods and agreeing plans for dissemination of the study results to participants and wider relevant communities? You may find this link helpful.

In addition to considering the points above we advise authors to look at guidance for best reporting of patient and public involvement as set out in the GRIPP2 reporting checklist.  

If information detailing whether there was patient and public involvement, or not, is missing in the submitted manuscript we will request authors to provide it.

Where they have been involved we consider it good practice for authors to name and thank them in the contributorship statement after seeking their permission to do so; and to clearly identify them as patient/public contributors. When they have contributed substantially and meet authorship criteria they should be invited to coauthor the manuscript.

Links to selected examples of Patient and Public Involvement statements in published BMJ research papers showing patient and carer involvement at various stages of the research process.

Comparison of the two most commonly used treatments for pyoderma gangrenosum: results of the STOP GAP randomised controlled trial

Evidence based community mobilization for dengue prevention in Nicaragua and Mexico

Computerised cognitive behaviour therapy (cCBT) as treatment for depression in primary care (REEACT trial): large scale pragmatic randomised controlled trial .

Real world effectiveness of warfarin among ischemic stroke patients with atrial fibrillation: observational analysis from Patient-Centered Research into Outcomes Stroke Patients Prefer and Effectiveness Research (PROSPER) study.

Example PPI statements to adapt for use in a paper

Examples to guide the wording for PPI statements

Data sharing

We require a data sharing statement for all research papers. For papers that do not report a trial, we do not require that the authors agree to share the data, just that they say whether they will.

For reports of clinical trials, we ask that the authors commit to making the relevant anonymised patient level data available on reasonable request (see editorial ). This policy applies to any research article that reports the main endpoints of a randomised controlled trial of one or more drugs or medical devices in current use, whether or not the trial was funded by industry.

"Relevant data" encompasses all anonymised data on individual patients on which the analysis, results, and conclusions reported in the paper are based. As for "reasonable request," The BMJ is not in a position to adjudicate, but we will expect requesters to submit a protocol for their re-analysis to the authors and to commit to making their results public. We will encourage those requesting data to send a rapid response to thebmj.com, describing what they are looking for. If the request is refused we will ask the authors of the paper to explain why.

In addition, we will follow the new ICMJE data sharing policy that goes into place on July 1, 2018 (see editorial ): manuscripts submitted to ICMJE journals that report the results of clinical trials must contain a data sharing statement that indicates whether individual de-identified participant data (including data dictionaries) will be shared; what data in particular will be shared; whether additional, related documents will be available (study protocol, statistical analysis plan, etc); when the data will become available and for how long; by what access criteria data will be shared (including with whom, for what types of analyses, and by what mechanism). Clinical trials that begin enrolling participants on or after January 1, 2019 must also include a data sharing plan in the trial’s registration. If the data sharing plan changes after registration this should be reflected in the statement submitted and published with the manuscript, and updated in the registry record.

We encourage authors of all research articles in The BMJ to link their articles to the raw data from their studies. For clinical trials, we require data sharing on request as a minimum and- if authors of such trials are willing to go further and share the data openly, so much the better. The BMJ has partnered with the Dryad digital repository datadryad.org to make open deposition easy and to allow direct linkage by doi from the dataset to The BMJ 's article and back (for The BMJ 's articles' datasets see here ).

Data requesters should do the following: • Submit a rapid response to the paper and email the corresponding author for the paper to request the relevant data. • Be prepared to provide the authors of the paper a detailed protocol for your proposed study, and to supply information about the funding and resources you have to carry out the study. • If appropriate, invite the original author[s] to participate in the re-analysis. • If a month elapses without a response from the authors, please email the head of research for The BMJ (presently [email protected] ) and cc [email protected] . • The BMJ will assess the request and if appropriate we will encourage the authors or their institution to share the data, although we are not in a position to compel data release or broker agreements. Our role is limited to making the request process public, and all correspondence related to the request may be made public through rapid responses to the paper.

Statements that must be included in Research submissions (Ethics approval, funding, and transparency)

Ethics approval

All research studies published in The BMJ should be morally acceptable, and must follow the World Medical Association's Declaration of Helsinki . To ensure this, we aim to appraise the ethical aspects of any submitted work that involves human participants, whatever descriptive label is given to that work including research, audit, and sometimes debate. This policy also applies on the very rare occasions that we publish work done with animal participants. The manuscript must include a statement that the study obtained ethics approval (or a statement that it was not required), including the name of the ethics committee(s) or institutional review board(s), the number/ID of the approval(s), and a statement that participants gave informed consent before taking part.

Transparency statement

Please include in your manuscript a transparency declaration : a statement that the lead author (the manuscript's guarantor) affirms that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as originally planned (and, if relevant, registered) have been explained.

The BMJ is committed to making the editorial process transparent and ethical. The BMJ ’s transparency policies are accessible from this link .

Role of the funding source

Please include in the manuscript a statement giving the details of all sources of funding for the study. As appropriate, the statement must include a description of the role of the study sponsor(s) or funder(s), if any, in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. In addition, the statement must confirm the independence of researchers from funders and that all authors, external and internal, had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis is also required.

If you are submitting an original article reporting an industry sponsored clinical trial, postmarketing study, or other observational study please follow the guidelines on good publication practice (GPP2) and on properly reporting the role of professional medical writers. Another resource, the Authors' Submission Toolkit: A practical guide to getting your research published summarises general tips and best practices to increase awareness of journals' editorial requirements, how to choose the right journal, submission processes, publication ethics, peer review, and effective communication with editors - much of which has traditionally been seen as mysterious to authors.

The BMJ will not consider for publication any study that is partly or wholly funded by the tobacco industry, as explained in this editorial .

Patient and Public Involvement statement

Within the Methods section of your paper, please state if and how patients and the public were involved in the research you are describing. For more information, please see the specific guidance on mandatory reporting of patient and public involvement above. If patients and the public were not involved this information should be formally documented in the Patient and Public Involvement statement.

Dissemination to participants and related patient and public communities

For accepted papers we will ask you to confirm when and how the results of your study were (or will be) sent to research participants and whether they are also being sent to relevant patient and public communities, as applicable. If you have not disseminated and have no plans to do so, please state why.

Summary boxes

Please produce a box offering a thumbnail sketch of what your article adds to the literature. The box should be divided into two short sections, each with 1-3 short sentences.

Section 1: What is already known on this topic

In two or three single sentence bullet points, please summarise the state of scientific knowledge on this topicbefore you did your study, and why this study needed to be done. Be clear and specific, not vague.

Section 2: What this study adds

In one or two single sentence bullet points, give a simple answer to the question “What do we now know as a result of this study that we did not know before?” Be brief, succinct, specific, and accurate. For example: "Our study suggests that tea drinking has no overall benefit in depression." You might use the last sentence to summarise any implications for practice, research, policy, or public health. For example, your study might have asked and answered a new question (one whose relevance has only recently become clear); contradicted a belief, dogma, or previous evidence provided a new perspective on something that is already known in general; or provided evidence of higher methodological quality for a message that is already known. DO not make statements that are not directly supported by your data.

Additional information that must be included with reports of Clinical Trials

Trial registration

In accordance with the International Committee of Medical Journal Editors' Recommendations for the Conduct, Reporting, Editing, and Publication of Scholarly Work in Medical Journals , The BMJ will not consider reports of clinical trials unless they were registered prospectively before recruitment of any participants. This policy on prospective registration applies to trials that started after 1 July 2005; for older trials retrospective registration will be acceptable, but only if completed before submission of the manuscript to the journal. The trial registration number and name of register should be included as the last line of the structured abstract. The BMJ accepts registration in any registry that is a primary register of the WHO International Clinical Trials Registry Platform (ICTRP) or in ClinicalTrials.gov , which is a data provider to the WHO ICTRP.

In your submission, please include details about registration: registry, date registered, affirmation that registration was prospective before enrolling the first patient (if applicable) and registry number. The BMJ relies on information contained in trial registries. If authors believe that information in the registry is incorrect they should make their case to registry officials.

Eligible trials have been defined by ICMJE since 1 July 2008 as trials "where human participants are prospectively assigned to one or more health-related interventions (including health services and behavioural interventions) to evaluate the effects on health outcomes," and before that were defined more narrowly as trials "where human participants are prospectively assigned to investigate the cause and effect relationship between a medical intervention and health outcome." The ICMJE further states that, "Some trials assign healthcare providers, rather than patients, to intervention and comparison/control groups. If the purpose of the trial is to examine the effect of the provider intervention on the health outcomes of the providers' patients, then investigators should register the trial. If the purpose is to examine the effect only on the providers (for example, provider knowledge or attitudes), then registration is not necessary." We will take these definitions into account when evaluating if trials were adequately registered.

The BMJ does not consider posting of protocols and results in clinical trial registries to be prior publication. We also will consider research articles that have been posted on preprint servers, provided this is clearly disclosed on submission of the paper.

The BMJ encourages but does not require registration of protocols and posting of results in publicly accessible registries for studies that are not clinical trials if they involve human participants, particularly observational studies . If the study was registered, please provide the registration details, explaining whether the study was registered before data acquisition or analysis began.

The BMJ expects authors of clinical trials to report their findings in accordance with the outcomes listed in the trial registry. Outcomes that were not pre-specified in the registration should be identified as such in the text of the paper and in any tables. All registered outcomes should be described in the BMJ paper. If results for any outcomes will be or have been reported in another publication this should be made clear to readers. The timing and reasons for any changes in registered outcomes should also be disclosed.

The BMJ requires authors of clinical trials to upload a protocol for their study. This protocol will be published alongside other materials if the article is accepted. Any discrepancies between the protocol-specified outcomes and those listed in the trial registry or reported in the paper should be explained in the paper. In cases where pre-specified outcomes differ between the trial registration and the protocol, our policy is to consider the outcomes listed in the registry as pre-specified. Outcomes listed in the protocol but not the trial registry can be reported in the paper, but should be identified as post-hoc outcomes. Protocols vary in completeness and content. There are often multiple versions of a protocol and the timing of decisions about outcomes in relation to the onset of a trial cannot easily be determined. This is in contrast to trial registries, where date stamps are reliable and can be easily verified by readers.Trial registry entries should be updated if new outcomes are added or existing ones deleted, promoted, or demoted.

The BMJ requires authors of clinical trials to upload a statistical analysis plan (SAP) for their study. The SAP will be published alongside other materials if the article is accepted. A SAP provides more detailed information about statistical analysis than a protocol, including detailed descriptions of procedures used to execute the analyses. Please follow the guidance on producing a SAP contained in the table of this document: https://jamanetwork.com/journals/jama/fullarticle/2666509

Open access

Research papers in The BMJ are published with open access. Moreover, The BMJ immediately fulfils the requirements of the US National Institutes of Health, the UK Medical Research Council, the Wellcome Trust, and other funding bodies by making the full text of publicly funded research freely available to all on bmj.com and sending it directly to PubMed Central, the National Library of Medicine's full text archive. The BMJ occasionally publishes as open access other types of (non-research) articles arising from work funded by a funder who mandates open access publication.

Open access articles may be reused according to the relevant Creative Commons licence. The BMJ 's default licence for open access publication of research is the Creative Commons Attribution Non Commercial licence (CC BY-NC 4.0) . But where the funder requires it the author can select the Creative Commons Attribution (CC BY 4.0) licence during the submission process (funders who mandate CC BY include the Wellcome Trust, RCUK, and MRC).

To support this, we ask authors to pay an open access article processing charge - you can find our author charges for open access here . We can offer discounts and waivers for authors who cannot pay. Consideration of the paper is not related to whether authors can or cannot pay the fee. We will ask for the fee only once we have accepted a paper, and we will send an invoice only once authors tell us (via [email protected] ) they can claim the fee. Seeking and processing fees will not delay editing or publication. Please do not contact editors about open access fees: neither editors nor reviewers will know whether a fee is payable, and administrative staff will handle payments and all associated correspondence. For non-research articles published with open access we will ask authors to pay the open access fee. We do not offer refunds for Open Access once articles have been published. For further information, contact [email protected] .

A number of institutions have open access institutional memberships with BMJ (the publishing group), which either cover the whole cost of open access publishing for authors at participating institutions or allow authors to receive a discount on the article processing charge. For a list of member institutions and their policies on how to receive a discount or to publish free of charge, please visit http://journals.bmj.com/site/authors/openaccess.xhtml

For articles not published with open access, The BMJ 's publication licence allows each author to post their article's URL (provided above) on either their own or their employer's website, thereby giving users free access to the full text of the article on bmj.com. Authors will need to use the toll free link to ensure visitors have free access to the article. Alternatively, authors can post the full text of their published article on their own website or their employer's website.

For additional information, please see the section of instructions to authors on copyright, open access, and permission to reuse .

Living systematic reviews

The BMJ will pilot a small number of living systematic reviews

Duration : We will typically host a living systematic review which is live for up to 2 years after initial publication. The triggers for updates, and their frequency, will be decided with authors on a case by case basis. Communication : The title will reflect the living nature of the review and the most recent update will become the default publication on bmj.com. Reviews will have a single digital object identifier (DOI) to keep the information in one place. However, previous versions will remain available as data supplements. An updates table will be included in the review to make tracking the history of the review easier and to signal planned changes. Updates will be flagged on bmj.com, including in rapid responses. They will also be communicated to third parties including PubMed and PubMedCentral. Updates : Updates should be submitted as a “track changes” version of the final MIcrosoft Word version of the previous iteration of the review. A clean version should also be submitted via the ScholarOne manuscript system. Subsequent internal or external peer review reports will be added to the pre-publication history tab on bmj.com with each version of the paper. The approach to any authorship changes should be negotiated before the first version of the paper is published. Resources : The usual BMJ article open access processing fee will be charged for the initial version of the review and an additional fee will be added to cover the cost of up to three updates per year (£2000 per update). After the first year the price may be revised based on the scope of the revisions and the work done on each one.

Preliminary reporting guidance for living reviews

COVER LETTER: This should explain and defend the need for the review to be “living.” Briefly describe other extant reviews, in particular any other living systematic reviews that have recently been published. The cover letter should acknowledge the authors’ acceptance of the following special conditions that apply to living reviews: 1) the need to provide current conflict of interest declarations or updates for all authors at each revision; 2) the single DOI for the paper and updates; agreement that open access fees cannot be waived for living reviews and that additional fees apply to cover the extra work of producing and maintaining living reviews.

TITLE: The phrase “living systematic review” should appear in the title. If additional terms apply, those may be included as appropriate (e.g. “network meta-analysis,” “meta-analysis,” “critical appraisal,” etc.).

ABSTRACT: The abstract should include: 1) A statement of the research question or objective, including a statement that one objective is to provide regular updates and keep the review live. 2) The rationale for a living systematic review should be described, e.g. rapidly evolving evidence base, anticipated impact on policy or practice, etc. 3) A “Readers’ note” at the end of the abstract that provides information about the version of the paper, the date it went live, and gives notice of planned updates. For example: “Readers’ note: This article is a living systematic review that will be updated periodically over the next 2 years to reflect emerging evidence. This version is update XXX of the original article published XXXXXX (give BMJ DOI), and previous updates can be found as data supplements (give link). When citing this paper please consider adding the version number and date of access for clarity.”

MAIN PAPER: Please address the following matters in the appropriate section of the paper: Introduction: -- Include the information required in the abstract (see above paragraph) at the end of the introduction section. -- In updates, consider including a short paragraph that describes how the living review has evolved. For example, what are the key developments since the previous version of the review, and what developments might be expected? Methods -- Mention and include a reference to any published or publicly available protocol for this review. If not registered, consider registering the review. -- Describe the methods that will be used to keep the review living, including the processes that will be used to search for new evidence, anticipated triggers for updates, and the circumstances under which the review might end before the 2 year time limit for BMJ Living Reviews. -- In updated versions of the review, make clear when and why any methods have evolved over time. If these descriptions are lengthy or complex, consider doing this in a table that can be included in an appendix or supplemental file. Such a table will ideally describe important changes to the review protocol, statistical analyses, or other aspects of the review, along with the dates of these changes. -- A table at the end of the discussion section might be used to highlight new evidence that was not included in the review. Results -- Clearly state the updated dates of the search. Discussion -- Consider additional subheadings to separate, e.g. What remain the important findings so far? Versus what are the main new findings to highlight? -- Consider additional table updates to this article. This will make clear historical and anticipated change. Columns trigger, date and action. Declaration of competing interests -- All authors must complete the ICMJE Competing Interests form with the initial submission. At each revision, we will ask the corresponding author to state whether there have been any changes to competing interests among any of the existing authors. If there are changes or if new authors have been added, the corresponding author is responsible for ensuring the this information is up to date. Otherwise there will be no change to the declaration of interests. Supplementary files -- Previous versions of the paper

Please contact Dr. Elizabeth Loder ( [email protected] ) with any questions.

Supplemental material, video

You may submit the following materials as supplemental files if you think they will help the authors and reviewers make a decision or readers better understand your study:

Original raw data if you think they will help our reviewers (and maybe readers), or if we specifically request them. Please note our policy on data sharing, explained above.

Video and audio files that will add educational value to your article, for example by explaining the intervention in a trial.

A video abstract that summarizes your findings and that will be posted on bmj.com with your paper. You can find additional information about video abstracts here and here .

Public and patient involvement materials used in your research.

Copies of any non-standard questionnaires and assessment schedules used in the research.

Copies of patient information sheets used to obtain informed consent for the study or to comprise or deliver the intervention in a clinical trial.

Copies of closely related articles you have published (this is particularly important when details of the study methods are published elsewhere).

Copies of any previous reviewers' reports on this article . We appreciate that authors may have tried other journals before sending their work to The BMJ , and find it helpful if you let us know how you have responded to previous reviewers' comments.

Research Methods and Reporting (RMR)

We are willing to consider papers that present new or updated research reporting guidelines, but only if the guideline pertains to a study type that we publish in The BMJ. The checklist itself must be included as part of the paper. We prefer to be the only journal publishing the guideline, but under some circumstances we will consider co-publication with up to two other journals. For an example of how to format a reporting guideline to appear in our research methods and reporting section, see http://www.bmj.com/content/346/bmj.f1049.full.pdf+html .

Preparing a RMR article

Word count We do not set fixed word count limits for RMR articles. Nonetheless, we ask you to make your article concise and make every word count. For some submissions this might be published in full on bmj.com with a shorter version in the print BMJ 

Overall structure Research Methods and Reporting should have the following elements:

Title and standfirst A short title is followed by an 100-150 word italicised single sentence (the standfirst) which encapsulates the article’s central message.

Introduction Articles should begin with a brief paragraph that captures readers’ attention and explains the aim of the piece.

Text The body of the text should be broken up under subheadings that provide a logical narrative structure. Avoid acronyms and abbreviations unless they are universally recognised e.g. DNA. The evidence on which key statements are based should be explicit and referenced, and the strength of the evidence (published trials, systematic reviews, observational studies, expert opinion etc.) addressed.

Boxes, tables and figures Include tables, boxes, or illustrations (clinical photographs, imaging, line drawings, and figures) to enhance the text and add to or substantiate key points made in the body of the article. Figures may be in color. Worked out examples that use specific methods under discussion can be included as additional boxes. If appropriate, include a box of linked information such as website urls for those who want to pursue the subject in more depth.

Web extras We may be able to publish on bmj.com some additional boxes, figures, and references (in a separate reference list numbered w1, w2,w3, etc. and marked as such in the main text of the article). Also may include suggestions for linked podcasts or video clips, as appropriate.

Contributors and sources We ask for a 100-150 word supplementary paragraph (excluded from word count) to explain the article’s provenance. It should include the relevant experience and expertise of each author, his or her contribution to the paper, and the sources of information used to prepare it. One author must be nominated as the guarantor of the article. Include a statement of sources and selection criteria.

Key messages box Include up to four sentences, in the form of bullet points, highlighting the article's main points.

References Must be in Vancouver style and should be kept to a minimum; ideally no more than 20.

“Analysis” is a distinct article type at The BMJ , and differs from other sections such as Research, Education, Editorials, and Personal Views. A great Analysis article makes an argument and supports it with reference to a robust (not cherry picked) evidence base. It has academic heft yet is a journalistic read. 'Academic heft' means the argument is evidence-based and supported by data. 'Journalistic read' means the article is really engaging (not dry nor dull; written in clear language and avoiding technical jargon; and pitched to our international audience of doctors of all specialties, academics, and policy makers). Keep in mind that Analysis articles are “long reads” at around 1800-2000 words, so they need to be absolutely great reading to keep readers’ attention, particularly readers that may not be familiar with the topic.

We receive many manuscripts that are not a good fit for the Analysis section. We generally do not consider:

• Case studies (e.g. where the article mostly concerns the author’s writing about their own work) • Manuscripts containing primary research data (such papers should be submitted as Research) • Narrative review articles (as a general practice, The BMJ does not accept unsolicited submissions of review articles) • Articles presenting a new hypothesis

If you are unsure if your work is suitable for The BMJ 's Analysis section we are willing to consider succinct pre-submission inquiries, please complete the form in this link and await a response from one of the analysis editors.

Preparing an Analysis article

We recommend looking at this Analysis article template and using it as a basis for your work before considering submission.

Word count and style The BMJ has an international readership that includes policy makers, health professionals, and doctors of all disciplines. Authors are advised to keep this readership in mind and to write their article for the non-expert. It’s important to avoid jargon. Specialised terminology and references to organisations or practices that are specific to one country need to be explained. Clear writing and an attractive presentation are essential. Analysis papers should be 1,800-2,000 words long.

Overall structure The manuscript should have the following elements:

Title and standfirst A short title is followed by an italicised single sentence (the standfirst) which encapsulates the article’s central message.

Text The body of the text should be broken up under sub-headings that provide a logical narrative structure. Avoid acronyms and abbreviations unless they are universally recognised e.g. DNA. The evidence on which key statements are based should be explicit and referenced, and the strength of the evidence (published trials, systematic reviews, observational studies, expert opinion, etc.) made clear. Articles should present a balanced, even-handed look at the evidence rather than selectively citing evidence that supports a particular view.

Boxes, tables and figures These should extend and substantiate points made in the body of the paper. Words in boxes and tables are excluded from the word count of the body of the text, but the additional material should be concise.

Key messages box This should be at the end of the article and include 2 to 4 points summing up the main conclusions. When submitting your article at submit.bmj.com, please enter your key messages when prompted to enter the abstract.

Contributors and sources We ask for a 100-150 word supplementary paragraph (excluded from word count) to explain the article’s provenance. It should include the relevant experience and expertise of each author, his or her contribution to the paper, and the sources of information used to prepare it. One author must be nominated as the guarantor of the article.You are welcome to invite co-authors to work with you on the article. We suggest including 2-3 co-authors with different locations and perspectives to help ensure articles are international in scope and accessible to our broad readership online and in print.

Report of patient involvement As The BMJ is seeking to advance partnership with patients, we also ask authors to seek their input into articles wherever relevant, and document their involvement as patient contributors or coauthors.

Conflicts of Interest All authors should read our competing interests policy and include the appropriate declaration in their manuscript. Where a competing interest exists that might disqualify an author from contributing, it is wise to discuss it with a BMJ editor before writing the article.

Peer review The BMJ has fully open peer review for analysis articles. This means that every accepted analysis article submitted from February 2016 onwards will have its prepublication history posted alongside it on thebmj.com. This prepublication history comprises all previous versions of the manuscript, the report from the manuscript committee meeting, the reviewers’ signed comments, and the authors’ responses to all the comments from reviewers and editors. Authors are welcome to suggest names of suitable reviewers, including patient reviewers.

What happens after submission

What happens after publication.

In most cases we will publish the prepublication history alongside an accepted analysis article. This prepublication history comprises all previous versions of the manuscript, the report from the manuscript committee meeting, the reviewers’ comments, and the authors’ responses to all the comments from reviewers and editors. In rare instances we may determine after careful consideration that we should not make certain portions of the prepublication record publicly available. For example, in cases of stigmatised illnesses we seek to protect the confidentiality of reviewers who have these illnesses. In other instances there may be legal or regulatory considerations that make it inadvisable or impermissible to make available certain parts of the prepublication record. In all instances in which we have determined that elements of the prepublication record should not be made publicly available, we expect that authors will respect these decisions and also will not share this information.

Education (inc. Minerva Pictures and Endgames)

The BMJ publishes different types of educational articles to engage and challenge a range of postgraduate doctors and clinical researchers internationally. We strive to publish articles that are original in their content and/or presentation, and cannot be found elsewhere or in textbooks. We prioritise topics and situations that are common or have serious consequences, have international appeal, and that interest a variety of doctors, including GPs and specialists.

We encourage authors to write in teams, including those from other specialties, professions, and countries. We ask that one author is routed in the clinical environment of the intended reader. We encourage authors to write in plain English, to be clear about where there is uncertainty, and to include numbers and phrases where possible that will help doctors in conversation with their patients.

Our educational articles are shaped by two initiatives:

• We believe that financial interests can distort education articles and we minimise or exclude authors who we judge have such a conflict.

• We believe that patient involvement strengthens content. We encourage authors to seek input from patients either to inform the scope, develop the content, contribute to, or co-author articles. For help with this, please read our guidance on what we mean by patient involvement and co-production .

Submission process and presubmission enquiries

We receive more articles and suggestions than we can publish. We require all authors to contact us before submitting a manuscript to us. Send us your proposal using our Education Article Proposal Form , together with your completed Declaration of Financial Interests .

The proposal form will guide you through the following questions:

• What is your idea? • Can you sum up the aim of your article in a sentence? • Why is the topic important to The BMJ 's readers? • What is the prevalence of the symptom/condition/situation you wish to write about? • Why cover it now? Has something new happened? • What has The BMJ 's Education section covered on this topic in the last five years? What will your contribution add? • Can you provide the key evidence/references you might use? • Why are your writing team well placed to cover the topic? • Have you thought about what a patient would say about your idea?

Policies for Education articles

Authorship Education articles can have can have up to four authors. One author should be from the relevant specialty or setting, unless agreed otherwise. For example, if the article discusses presentation to the emergency department one author should be an emergency care doctor. All authors should meet authorship criteria . We welcome authors or contributions from allied health professions and patient authors, and actively encourage authors from a primary care background.

Competing interests The BMJ will not consider authors with financial interests when writing Education articles. It is important that we understand the financial interests of every author, and can judge to what extent we believe that they may be relevant to the article that you propose. We do not publish content from authors who we judge have relevant financial ties to the industry (excluding State of the Art reviews, Therapeutics articles, and Summaries of NICE Guidelines). The relevance of declared interests are judged by the BMJ team. This applies to every author. Any additional authors and their financial interests must be discussed and agreed with the commissioning editor before the article is submitted.

Patient involvement As part of our drive to co-produce our content with patients we ask that you seek patient input into articles at the planning stage. We believe that their experience and perspectives will make articles more useful for doctors in their quest to help improve patients well being and outcomes.

We ask all authors to what extent patients have been involved in their article and how their involvement changed the article. We ask that all writing encourages honesty and partnership with patients. Where uncertainty exists, share it. Where data exists present the numbers in a way that can be shared with the patient (use absolute numbers, natural frequencies, and graphics where you can). Use language that empowers patients to make the right choices for them in their situation (write that a doctor should/could offer a test, rather than should do a test).

When patients are involved in the manuscript, we ask for their consent. We have two types of consent forms for BMJ education articles:

• A patient consent form is required if any anonymised patient information is included in the review. Consent is needed for images even if the patients are not identifiable for example, in X-rays and histology slides, and for patients’ stories/vignettes even if details are anonymised.

• A patient contributor form is required for any patients who are named within the review, for example, patient co-authors, patient contributors or named authors of patient stories.

Preparing your manuscript

We want our readers to have the ability to share decisions with their patients and make clear for them the degree of certainty ( or lack of it) about a potential course of action. We therefore ask that, in addition to the format and instructions detailed below for the specific Education article that you are writing, you follow these recommendations:

• Consider including in your manuscript a box explaining your strategy to search for evidence. It should include a search date, the sources searched, and brief inclusion criteria. • Clearly distinguish suggestions made based on your experience, standard practice, guidelines, and evidence. • Provide specifics about the evidence you discuss. For example, for key statements, please say: "A large, well conducted, randomised controlled trial showed INSERT number [CI] and or p value". "The findings of a small case series suggest...". “A subgroup analysis found…”. etc. • Use absolute numbers or explain why you have not used them. • Consider how these numbers can be communicated by the clinician read to their patient in a clear way. • Where evidence is lacking or of poor quality make this clear. • Write about known and unknown benefits and harms.

"What you need to know" box . No more than three bullet points for practice articles and five for clinical updates encapsulating the specific take home messages from this article.

"How patients were involved in the creation of this article" box. Please include: Which patients were asked (e.g. patient advocates, networked patient communities and organisations, patients in your clinic etc). What they said (e.g. include more practical advice on how to inject insulin.) How you changed your article as a result (e.g. we included a box to address this.)

"Education into practice" box . Include two to three bullet points about how a reader might at an individual or organisational level improve their practice (e.g. do you offer lifestyle advice to all patients with newly diagnosed hypertension?)

At least one other box or table and at least one figure or image that complement the text of the article.

Article types

We accept pitches for the following article types. Once our editors have made a decision to encourage a pitch, we will provde authors will a full, detailed set of instructions on how best to format your content.

Additional requirements for all other article types

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Methodology of a systematic review


Context: The objective of evidence-based medicine is to employ the best scientific information available to apply to clinical practice. Understanding and interpreting the scientific evidence involves understanding the available levels of evidence, where systematic reviews and meta-analyses of clinical trials are at the top of the levels-of-evidence pyramid.

Acquisition of evidence: The review process should be well developed and planned to reduce biases and eliminate irrelevant and low-quality studies. The steps for implementing a systematic review include (i) correctly formulating the clinical question to answer (PICO), (ii) developing a protocol (inclusion and exclusion criteria), (iii) performing a detailed and broad literature search and (iv) screening the abstracts of the studies identified in the search and subsequently of the selected complete texts (PRISMA).

Synthesis of the evidence: Once the studies have been selected, we need to (v) extract the necessary data into a form designed in the protocol to summarise the included studies, (vi) assess the biases of each study, identifying the quality of the available evidence, and (vii) develop tables and text that synthesise the evidence.

Conclusions: A systematic review involves a critical and reproducible summary of the results of the available publications on a particular topic or clinical question. To improve scientific writing, the methodology is shown in a structured manner to implement a systematic review.

Keywords: Meta-analysis; Metaanálisis; Methodology; Metodología; Revisión sistemática; Systematic review.

Copyright © 2018 AEU. Publicado por Elsevier España, S.L.U. All rights reserved.

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Systematic Reviews

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Types of Reviews

Review Typologies

There are many types of evidence synthesis projects, including systematic reviews as well as others. The selection of review type is wholly dependent on the research question. Not all research questions are well-suited for systematic reviews.

Review the table to peruse review types and associated methodologies. Librarians can also help your team determine which review type might be appropriate for your project. 

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108.  doi:10.1111/j.1471-1842.2009.00848.x

systematic review article type

Systematic Reviews & Other Review Types

What is a Systematic Review?

Systematic Review vs. Literature (Narrative) Review

Traditional literature review / narrative review:



Systematic review:

Source: Cochrane. Background to Systematic Reviews

This link will open a PDF document. 



Level of Evidence pyramid

A systematic review is defined as “a review of the evidence on a clearly formulated question that uses systematic and explicit methods to identify, select and critically appraise relevant primary research, and to extract and analyze data from the studies that are included in the review.”  The methods used must be reproducible and transparent.

Source: Undertaking Systematic Reviews of Research on Effectiveness. CRD’s Guidance for those Carrying Out or Commissioning Reviews. CRD Report Number 4 (2nd Edition). NHS Centre for Reviews and Dissemination, University of York. March 2001.  

Image: EBM Pyramid and EBM Page Generator, copyright 2006 Trustees of Dartmouth College and Yale University. All Rights Reserved.  Produced by Jan Glover, David Izzo, Karen Odato and Lei Wang.

When is a Systematic Review the most appropriate study design?

When answering questions of effectiveness comparing two different treatments or interventions.

Is your review question a complex intervention? Learn more about Reviews of Complex Interventions . 

Choosing a Review Type: This guide explains other comprehensive literature reviews of similar methodology to the systematic review.

Here is a helpful article about review types.  ( Meeting the Review Family: Exploring review types and associated information retrieval requirements,  2019,Sutton et al.)

You may also find the Review Ready Reckoner helpful! 

7 Stages of Conducting a Systematic Review

1.  Gathering your team (Minimum of two reviewers with a third to serve as a tiebreaker)

A systematic review must have a team of two or greater. A systematic review cannot be completed by one person. Choose team members wisely and based on areas of expertise. A third team member is sometimes called a tiebreaker. They are to resolve disagreements for reviewers 1 and 2 for stages of the review that are blinded (screening, data extraction, critical appraisal) and are completed by two independent reviewers.

2.  Questioning (Define a narrow question, may use PICO)  

The PICO format is commonly used to define the research question into one that is a searchable question. In some cases, the PICO format may not work and another format can be used. The P in PICO is Patient/Problem or Person. I is for Intervention/Exposure/Therapy or Treatment. C is optional and is for Comparison (such as a placebo or another drug/therapy) and O is for Outcome(s), what is the expected or anticipated outcome you will find in the literature? A systematic review question should be narrow in scope. The purpose of a systematic review is to draw conclusions based on the evidence to answer that one well-defined and narrow question. 

3.  Planning (Create a protocol, plan methods & strategies, register protocol) * This course focuses on the planning stage 

Having a plan in place is essential to a good quality review and by spending more time planning before the review takes place, you could avoid issues or errors that may slow down the process or be detrimental to the review. Planning includes seeing if the review is feasible, checking to make sure there are no conflicting reviews and also ensuring that there is a plan to carry out each stage of the review. Setting goals and timelines for the review is important as well as mapping out how the review project will be managed. This is also put into a document called a protocol. Registering the protocol is optional but highly recommended. The protocol also includes defining a priori what the selection criteria will be for the review in terms of inclusion and exclusion criteria for what studies should be screened by for inclusion in the review. 

4.  Searching/Screening (Exhaustive, transparent & repeatable searching for evidence/selecting studies) 

Includes searching multiple databases, grey literature/clinical trial registries and handsearching of the literature (performed by the subject matter expert). It is best practice to involve a librarian or an information specialist in creating the comprehensive search, translating the search for databases or grey literature, documenting the search and deduplicating the repeating references in a citation manager and writing the search methods for the review. However, librarians are usually not involved in grey literature searching unless they are an expert in the subject matter. The review team member with the most subject matter expertise is the one who is best equipped to handsearch. The search stage may also include contacting other experts in the field to identify publications that have not been published yet. Systematic reviews include both published and unpublished literature to avoid a type of publication bias, called positive outcomes bias since positive outcomes are more likely to be published. Screening is done in two phases.  The first phase is screening titles/abstracts (together) and the second phase is screening full texts.  Screening is done independently by two reviewers, with a third reviewer serving as a tiebreaker. Reviewers should not move on to the full text screening phase until they have screened all of the titles and abstracts and each is a clear Yes or No without maybes remaining. Once they are ready to screen full texts, they must acquire and read all of the full texts and screen them based on the studies selection criteria. Only Yes's are included in the review but all No's must have a reason listed for exclusion. The new PRISMA 2020 requires reporting of study Near Misses too. Near misses are any studies that did not meet inclusion in the review but were very close to being included. Refer to the PRISMA 2020 http://www.prisma-statement.org/PRISMAStatement/ for more guidance on this stage. There are tools designed specifically to assist with the systematic review screening phase.

5.  Managing & reporting 

All methods must be fully reported, transparent and reproducible. The methods reported must also follow the recommended reporting guidance such as the PRISMA 2020. Reporting guidance can be identified by searching the Equator Network https://www.equator-network.org/ . Reporting guidance may be modified for review types similar to the systematic review. Refer to the many PRISMA 2020 extensions http://www.prisma-statement.org/Extensions/ for more information. 

6.  Data Extraction/Synthesizing the evidence  

This stage includes appraising the evidence, interpreting results, performing a qualitative (narrative analysis) and/or a quantitative/meta-analysis. A meta-analysis is optional and is only done if it is feasible. A biostatistician or advanced training in statistics is recommended if doing a meta-analysis. There are many tools designed to assist with this process. 

Evidence from studies is assessed using critical appraisal or Risk of Bias tools and/or checklists by study design. 

Critical appraisal tools from Temple University, Systematic Review Research Libguide

More tools for critical appraisal and other stages of the review from the National Collaborating Centre for Methods and Tools

Data from all studies must also be extracted and put into tables/charts such as the Summary of Findings (SOF) table and is reported as a narrative synthesis. Data is collected from all studies if conducting a meta-analysis and its numerical findings are reported. 

Here are some more detailed elaborations and examples:

Synthesis: Provide a narrative synthesis of the included studies individually and when combined (What are the differences and the commonality between studies?) or what can be demonstrated from the research when combining the studies together? A meta-analysis is optional. Create a data abstraction/extraction form for the purposes of collecting data that is similar across all included studies, include a ‘Characteristics of Studies’ table to show this data (see table example  and this example  (opens a PDF document) on page 48. Summary of Findings tables are provided starting on page 8 of the same document. Data extraction must be done using data extraction forms and independently/blinded by two reviewers, with a 3rd reviewer serving as a tiebreaker. 

7.  Drawing Conclusions, Writing & Publishing

After completing these steps, the results of the review must be shared. What is the level of evidence? Is there evidence in support of the question or are more studies needed to draw conclusions? What are your recommendations for future studies? What are the limitations to your systematic review? How do these findings from your review change what is known on the topic or question?


Discuss what contribution this review makes and how your review answers or addresses the original question. Discuss any gaps found in the research. Make recommendations for needed research to address these gaps and the importance of addressing them. Discuss the overall strength of evidence in support of your original question (strong, moderate or weak). 

For more guidance on the systematic review stages, refer to the Cochrane Handbook (medicine/health sciences), the JBI Manual (health sciences/nursing) or the methods guides for Campbell Collaboration Systematic Reviews (Business, education, social welfare, criminal & justice topics and more). 

Where to register your Systematic Review Protocol?

Moller AM, Myles PS.   What makes a good systematic review and meta-analysis?   BJA.  2016. 117(4):428-430.

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Systematic Reviews: What is a systematic review?

What is a Systematic Review?

In the health-related professions, systematic reviews are considered the most reliable resources.  They are studies that make up the top level of the evidence-based information pyramid, and as a result, they are the most sought after information for questions about health. Systematic reviews are not quite the same as literature reviews. Literature reviews, also known as narrative reviews, attempt to find all published materials on a subject, whereas systematic reviews try to find everything that focuses on answering a specific question.  Since systematic reviews are generally associated with health related fields, their main objective is to ensure the results of the review provide accurate evidence that answers relevant questions.  If you are looking for information about literature reviews, please check the library's guide on the topic  here .

Why use systematic reviews to answer questions?

When looking for answers to health questions, systematic reviews are considered the best resources to use for evidence-based information.  The predefined protocols, the amount of information reviewed, the evaluation process involved, and the efforts to eliminate bias are all a part of what makes health professionals consider systematic reviews to be the highest level of evidence based information available.  As a part of the process, systematic reviews tend to look at and evaluate all the randomized controlled trials, or all the cohort studies, for their specific topic.  By looking at and evaluating a vast amount of comparable studies, a systematic review is able to provide answers that have a much stronger level of evidence than any individual study.

Why perform a systematic review?

These reviews collect large amounts of information that fit within the predetermined parameters, so performing a systematic review is an excellent way to develop expertise on a topic.  Setting up the criteria, searching for the information, and evaluating the information found, gives the reviewer an extremely strong understanding of the process needed to create a review as well as how to evaluate its various elements.  Creating a systematic review gives the reviewer an opportunity to further the discussion on a topic.  In the health fields, performing and then publishing these reviews provides more evidence on topics that can be used for making decisions in a clinical environment.

How to find a systematic review

There are a number of databases that focus on health related resources, and most of them search through journals that include systematic reviews.  In these cases, you can include the words “systematic review” and the results will include entries that have the words “systematic review” in them somewhere.  Many of these results will be systematic reviews; however, some of the results may include these words, but are not systematic reviews.  A few databases that are used by researchers have added in limitation features that make it easier to find systematic reviews, and ensure a specific article/document/publication type are found.  Here are three examples of databases and how to limit their search results to systematic reviews:

Types of systematic reviews

These are a few of the various types of systematic reviews.

Critical review

Critical reviews are often thought to be the same as a literature review.  They involve a comprehensive review of a topic that involves a high level of analysis that seeks to identify the most important aspects of a subject.

The overview is a look at the literature available on the topic.  They may or may not have an analytical component that provides a synthesis of the information found, but this depends on how systematic the review has been.

Qualitative systematic review

This type of study looks at as many qualitative studies and tries to find themes among these studies that lie across the range of reviews. The information is then organized into a narrative that is frequently accompanied by a conceptual model.

Rapid review

The number of studies included in a rapid review are dictated by time constraints. Most often these reviews are conducted to determine what is known about policies or practices, and then determine how much these are based on evidence.

Scoping review

These reviews are intended to quickly assess the availability of research on a specific topic, and then determine whether the evidence provided in these research articles is sufficient and appropriate, 

Umbrella review

Umbrella reviews research broad topic, and look at a wide range of reviews that have been done for a number of potential interventions. It then triest to establish the pros and cons of each treatment and what the potential results would be.

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Evidence-Based Research: Evidence Types


Systematic review, guidelines & summaries, randomized controlled trial, cohort study, case-controlled studies, background information & expert opinion.

Not all evidence is the same, and appraising the quality of the evidence is part of evidence-based practice research. The hierarchy of evidence is typically represented as a pyramid shape, with the smaller, weaker and more abundant research studies near the base of the pyramid, and systematic reviews and meta-analyses at the top with higher validity but a more limited range of topics.

Several versions of the evidence pyramid have evolved with different interpretations, but they are all comprised of the types of evidence discussed on this page. Walden's Nursing 6052 Essentials of Evidence-Based Practice class currently uses a simplified adaptation of the Johns Hopkins model .

Evidence Levels:

Level I:  Experimental, randomized controlled trial (RCT), systematic review RTCs with or without meta-analysis

Level II:  Quasi-experimental studies, systematic review of a combination of RCTs and quasi-experimental studies, or quasi-experimental studies only, with or without meta-analysis

Level III:  Nonexperimental, systematic review of RCTs, quasi-experimental with/without meta-analysis, qualitative, qualitative systematic review with/without meta-synthesis  (see Daly 2007 for a sample qualitative hierarchy) 

Level IV : Respected authorities’ opinions, nationally recognized expert committee or consensus panel reports based on scientific evidence

Level V:  Literature reviews, quality improvement, program evaluation, financial evaluation, case reports, nationally recognized expert(s) opinion based on experiential evidence

What is a Systematic Review?

A systematic review is a type of publication that addresses a clinical question by analyzing research that fits certain explicitly-specified criteria. The criteria for inclusion is usually based on research from clinical trials and observational studies. Assessments are done based on stringent guidelines, and the reviews are regularly updated. These are usually considered one of the highest levels of evidence and usually address diagnosis and treatment questions.

Benefits of Systematic Reviews

Systematic reviews refine and reduce large amounts of data and information into one document, effectively summarizing the evidence to support clinical decisions. Since they are typically undertaken by a entire team of experts, they can take months or even years to complete, and must be regularly updated. The teams are usually comprised of content experts, an experienced searcher, a bio-statistician, and a methodologist. The team develops a rigorous protocol to thoroughly locate, identify, extract, and analyze all of the evidence available that addresses their specific clinical question.

As systematic reviews become more frequently published, concern over quality led to the PRISMA Statement to establish a minimum set of items for reporting in systematic reviews and meta-analyses.

Many systematic reviews also contain a meta-analysis.

What is a Meta-Analysis?

Meta-analysis is a particular type of systematic review that focuses on selecting and reviewing quantitative research. Researchers conducting a meta-analysis combine the results of several independent studies and reviews to produce a synthesis where possible. These publications aim to assist in making decisions about a particular therapy.

Benefits of Meta-Analysis

A meta-analysis synthesizes large amounts of data using a statistical examination. This type of analysis provides for some control between studies and generalized application to the population.

To learn how to find systematic reviews in the Walden Library, please see the Levels of Evidence Pyramid page:

Further reading

Practice Guidelines

A practice guideline is a systematically-developed statement addressing common patient health care decisions in specific clinical settings and circumstances.  They should be valid, reliable, reproducible, clinically applicable, clear and flexible. Documentation must be included and referenced. Practice guidelines may come from organizations, associations, government entities, and hospitals/health systems.

Best Evidence Topics

Best evidence topics are sometimes referred to as Best BETs. These topics are developed and supported for situations or setting when the high levels of evidence don't fit or are unavailable. They originated from emergency medicine providers' need to conduct rapid evidence-based clinical decisions.

Critically-Appraised Topics

Critically-appraised topics are a standardized one- to two-page summary of the evidence supporting a clinical question. They include a critique of the literature and statement of relevant results. They can be found online in many repositories.

To learn how to find critically-appraised topics in the Walden Library, please see the Levels of Evidence Pyramid page:

Critically-Appraised Articles

Critically-appraised articles are individual articles by authors that evaluate and synopsize individual research studies. ACP Journal Club is the most well known grouping of titles that include critically appraised articles.

To learn how to find critically-appraised articles in the Walden Library, please see the Levels of Evidence Pyramid page:

A randomized controlled trial (RCT) is a clinical trial in which participants are randomly assigned to either the treatment group or control group. This random allocation of participants helps to reduce any possible selection bias and makes the RCT a high level of evidence. Having a control group, which receives no treatment or a placebo treatment, to compare the treatment group against allows researchers to observe the potential efficacy of the treatment when other factors remain the same. Randomized controlled trials are quantitative studies and are often the only studies included in systematic reviews.

To learn how to find randomize controlled trials, please see our CINAHL & MEDLINE help pages:

A cohort study is an observational longitudinal study that analyzes risk factors and outcomes by following a group (cohort) that share a common characteristic or experience over a period of time.

Cohort studies can be retrospective, looking back over time at data that has already been collected, or can be prospective, following a group forward into the future and collecting data along the way.

While cohort studies are considered a lower level of evidence than randomized controlled trials, they may be the only way to study certain factors ethically. For example, researchers may follow a cohort of people who are tobacco smokers and compare them to a cohort of non-smokers looking for outcomes. That would be an ethical study. It would be highly unethical, however, to design a randomized controlled trial in which one group of participants are forced to smoke in order to compare outcomes.

To learn how to find cohort studies, please see our CINAHL and MEDLINE help pages:

Case-controlled studies are a type of observational study that looks at patients who have the same disease or outcome. The cases are those who have the disease or outcome while the controls do not. This type of study evaluates the relationship between diseases and exposures by retrospectively looking back to investigate what could potentially cause the disease or outcome.

To learn how to find case-controlled studies, please see our CINAHL and MEDLINE help pages:

Background information and expert opinion can be found in textbooks or medical books that provide basic information on a topic. They can be helpful to make sure you understand a topic and are familiar with terms associated with it.

To learn about accessing background information, please see the Levels of Evidence Pyramid page:

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Systematic Review | Definition, Example & Guide

Published on June 15, 2022 by Shaun Turney . Revised on December 7, 2022.

A systematic review is a type of review that uses repeatable methods to find, select, and synthesize all available evidence. It answers a clearly formulated research question and explicitly states the methods used to arrive at the answer.

They answered the question “What is the effectiveness of probiotics in reducing eczema symptoms and improving quality of life in patients with eczema?”

In this context, a probiotic is a health product that contains live microorganisms and is taken by mouth. Eczema is a common skin condition that causes red, itchy skin.

Table of contents

What is a systematic review, systematic review vs. meta-analysis, systematic review vs. literature review, systematic review vs. scoping review, when to conduct a systematic review, pros and cons of systematic reviews, step-by-step example of a systematic review, frequently asked questions about systematic reviews.

A review is an overview of the research that’s already been completed on a topic.

What makes a systematic review different from other types of reviews is that the research methods are designed to reduce bias . The methods are repeatable, and the approach is formal and systematic:

Although multiple sets of guidelines exist, the Cochrane Handbook for Systematic Reviews is among the most widely used. It provides detailed guidelines on how to complete each step of the systematic review process.

Systematic reviews are most commonly used in medical and public health research, but they can also be found in other disciplines.

Systematic reviews typically answer their research question by synthesizing all available evidence and evaluating the quality of the evidence. Synthesizing means bringing together different information to tell a single, cohesive story. The synthesis can be narrative ( qualitative ), quantitative , or both.

Systematic reviews often quantitatively synthesize the evidence using a meta-analysis . A meta-analysis is a statistical analysis, not a type of review.

A meta-analysis is a technique to synthesize results from multiple studies. It’s a statistical analysis that combines the results of two or more studies, usually to estimate an effect size .

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A literature review is a type of review that uses a less systematic and formal approach than a systematic review. Typically, an expert in a topic will qualitatively summarize and evaluate previous work, without using a formal, explicit method.

Although literature reviews are often less time-consuming and can be insightful or helpful, they have a higher risk of bias and are less transparent than systematic reviews.

Similar to a systematic review, a scoping review is a type of review that tries to minimize bias by using transparent and repeatable methods.

However, a scoping review isn’t a type of systematic review. The most important difference is the goal: rather than answering a specific question, a scoping review explores a topic. The researcher tries to identify the main concepts, theories, and evidence, as well as gaps in the current research.

Sometimes scoping reviews are an exploratory preparation step for a systematic review, and sometimes they are a standalone project.

A systematic review is a good choice of review if you want to answer a question about the effectiveness of an intervention , such as a medical treatment.

To conduct a systematic review, you’ll need the following:

A systematic review has many pros .

Systematic reviews also have a few cons .

The 7 steps for conducting a systematic review are explained with an example.

Step 1: Formulate a research question

Formulating the research question is probably the most important step of a systematic review. A clear research question will:

A good research question for a systematic review has four components, which you can remember with the acronym PICO :

You can rearrange these four components to write your research question:

Sometimes, you may want to include a fifth component, the type of study design . In this case, the acronym is PICOT .

Their research question was:

Step 2: Develop a protocol

A protocol is a document that contains your research plan for the systematic review. This is an important step because having a plan allows you to work more efficiently and reduces bias.

Your protocol should include the following components:

If you’re a professional seeking to publish your review, it’s a good idea to bring together an advisory committee . This is a group of about six people who have experience in the topic you’re researching. They can help you make decisions about your protocol.

It’s highly recommended to register your protocol. Registering your protocol means submitting it to a database such as PROSPERO or ClinicalTrials.gov .

Step 3: Search for all relevant studies

Searching for relevant studies is the most time-consuming step of a systematic review.

To reduce bias, it’s important to search for relevant studies very thoroughly. Your strategy will depend on your field and your research question, but sources generally fall into these four categories:

At this stage of your review, you won’t read the articles yet. Simply save any potentially relevant citations using bibliographic software, such as Scribbr’s APA or MLA Generator .

Step 4: Apply the selection criteria

Applying the selection criteria is a three-person job. Two of you will independently read the studies and decide which to include in your review based on the selection criteria you established in your protocol . The third person’s job is to break any ties.

To increase inter-rater reliability , ensure that everyone thoroughly understands the selection criteria before you begin.

If you’re writing a systematic review as a student for an assignment, you might not have a team. In this case, you’ll have to apply the selection criteria on your own; you can mention this as a limitation in your paper’s discussion.

You should apply the selection criteria in two phases:

It’s very important to keep a meticulous record of why you included or excluded each article. When the selection process is complete, you can summarize what you did using a PRISMA flow diagram .

Next, Boyle and colleagues found the full texts for each of the remaining studies. Boyle and Tang read through the articles to decide if any more studies needed to be excluded based on the selection criteria.

When Boyle and Tang disagreed about whether a study should be excluded, they discussed it with Varigos until the three researchers came to an agreement.

Step 5: Extract the data

Extracting the data means collecting information from the selected studies in a systematic way. There are two types of information you need to collect from each study:

You should collect this information using forms. You can find sample forms in The Registry of Methods and Tools for Evidence-Informed Decision Making and the Grading of Recommendations, Assessment, Development and Evaluations Working Group .

Extracting the data is also a three-person job. Two people should do this step independently, and the third person will resolve any disagreements.

They also collected data about possible sources of bias, such as how the study participants were randomized into the control and treatment groups.

Step 6: Synthesize the data

Synthesizing the data means bringing together the information you collected into a single, cohesive story. There are two main approaches to synthesizing the data:

Generally, you should use both approaches together whenever possible. If you don’t have enough data, or the data from different studies aren’t comparable, then you can take just a narrative approach. However, you should justify why a quantitative approach wasn’t possible.

Boyle and colleagues also divided the studies into subgroups, such as studies about babies, children, and adults, and analyzed the effect sizes within each group.

Step 7: Write and publish a report

The purpose of writing a systematic review article is to share the answer to your research question and explain how you arrived at this answer.

Your article should include the following sections:

To verify that your report includes everything it needs, you can use the PRISMA checklist .

Once your report is written, you can publish it in a systematic review database, such as the Cochrane Database of Systematic Reviews , and/or in a peer-reviewed journal.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

A systematic review is secondary research because it uses existing research. You don’t collect new data yourself.

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Pharmacy : Types of Review Articles (Literature, Scoping and Systematic)

Their Uniqueness, Characteristics and Differences

The above slides explore:

Avoid duplication: register your scoping or systematic review protocol (plan)

Systematic Review Management Software

What is the Project's Goal?

Always ask yourself:

Conducting a comprehensive search of the literature involves very different methods than a systematic review. If you are unsure as to which project best meets your needs, consult the Pharmacy Liaison Librarian, Caitlin Carter at [email protected]

Literature (Narrative) Reviews

These resources offer practical insight into literature reviews:

Scoping Reviews

These resources offer practical insight into scoping reviews:

Systematic Reviews

These resources offer practical insight into systematic reviews:

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How to Write a Review Article

Descriptions of Types of Reviews

Reproduced from: Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies .  Health Info Libr J . 2009 Jun;26(2):91-108. doi: 10.1111/j.1471-1842.2009.00848.x. Review. PubMed PMID: 19490148.

Further Reading

Sutton A, Clowes M, Preston L, Booth A. Meeting the review family: exploring review types and associated information retrieval requirements . Health Info Libr J. 2019;36(3):202-222. doi: 10.1111/hir.12276.

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A young researcher's guide to a systematic review

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Key takeaways:

What is a systematic review?

A systematic review is a highly rigorous review of existing literature that addresses a clearly formulated question. The review systematically searches, identifies, selects, appraises, and synthesizes research evidence relevant to the question using methodology that is explicit, reproducible, and leads to minimum bias. Systematic reviews are regarded as the best source of research evidence. Systematic reviews are absolutely crucial in the field of evidence-based medicine, but are also highly valued in other fields.

A systematic review is more exhaustive than a literature review as it includes both published and unpublished literature, often called grey literature. Grey literature is a significant part of a systematic review and adds value to the review. This is because grey literature is often more current than published literature and is likely to have less publication bias. Grey literature includes unpublished studies, reports, dissertations, conference papers and abstracts, governmental research, and ongoing clinical trials.

Conducting a systematic review is a complex process. This article aims to guide you on the different kinds of systematic review, the standard procedures to be followed, and the best approach to conducting and writing a systematic review.

systematic review article type

Types of systematic reviews

Writing a protocol

Any good systematic review begins with a protocol. According to the National Institutes of Health (NIH) , a protocol serves as a road-map for your review and specifies the objectives, methods, and outcomes of primary interest of the systematic review. The purpose of having a protocol is to promote transparency of methods.

A protocol defines the search terms, inclusion and exclusion criteria, data that will be analyzed, etc. The protocol needs to be submitted to the journal along with your manuscript. Most journals expect authors of systematic reviews to use the PRISMA statement or similar other guidelines to write their protocol.

The PRISMA Statement:

Anybody writing a systematic literature review should be familiar with the PRISMA statement . The PRISMA Statement is a document that consists of a 27-item checklist  and a flow diagram and aims to guide authors on how to develop a systematic review protocol and what to include when writing the review.

A protocol ideally includes the following:

Registering systematic review protocols:

Once you have written your protocol, it is advisable to register it. Registering your protocol is a good way to announce that you are working on a review, so that others do not start working on it.

The available protocol registries for systematic reviews are:

The registries also provide a searchable database of registered reviews. Before starting a systematic review, you should search these databases for any registered reviews on the topic of your choice. This will ensure that you are not duplicating efforts.

What is the best approach to conducting a systematic review?

The essence of a systematic review lies in being systematic. A systematic review involves detailed scrutiny and analysis of a huge mass of literature. To ensure that your work is efficient and effective, you should follow a clear process :

1.  Develop a research question

2.  Define inclusion and exclusion criteria

3.  Locate studies 

4.  Select studies

5.  Assess study quality

6.  Extract data

7.  Analyze and present results

8.  Interpret results

9.  Update the review as needed

It is helpful to follow this process and make notes at each stage. This will make it easier for you to write the review article.

How is a systematic review article structured?

A systematic review article follows the same structure as that of an original research article. It typically includes a title, abstract, introduction, methods, results, discussion, and references.  

Title: The title should accurately reflect the topic under review. Typically, the words “a systematic review” are a part of the title to make the nature of the study clear.

Abstract: A systematic review usually has a structured Abstract, with a short paragraph devoted to each of the following: background, methods, results, and conclusion. 

Introduction : The Introduction summarizes the topic and explains why the systematic review was conducted. There might have been gaps in the existing knowledge or a disagreement in the literature that necessitated a review. The introduction should also state the purpose and aims of the review.

Methods: The Methods section is the most crucial part of a systematic review article. The methodology followed should be explained clearly and logically. The following components should be discussed in detail:

Results: The Results section should also be explained logically. You can begin by describing the search results, and then move on to the study range and characteristics, study quality, and finally discuss the effect of the intervention on the outcome.

Discussion: The Discussion should summarize the main findings from the review and then move on to discuss the limitations of the study and the reliability of the results. Finally, the strengths and weaknesses of the review should be discussed, and implications for current practice suggested.

References: The References section of a systematic review article usually contains an extensive number of references. You have to be very careful and ensure that you do not miss out on a single one. You can consider using reference management software to help you tackle the references effectively. 

You might also be interested in reading the folloowing related articles:

If you have any doubts or questions, you can post them in the comments section below. Alternatively, you can also a question on our Q&A forum  if you are facing a problem and need expert publication advice. 

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Systematic Review

Five other types of systematic reviews.

1. Scoping review

A scoping review is a preliminary assessment of the potential size and scope of available research literature. Aims to identify the nature and extent of research evidence (usually including ongoing research). 

Scoping reviews provide an understanding of the size and scope of the available literature and can inform whether a full systematic review should be undertaken. 

If you're not sure you should conduct a systematic review or a scoping review, this article outlines the differences between these review types and could help your decision making.  

2. Rapid review

Rapid reviews are an assessment of what is already known about a policy or practice issue by using systematic review methods to search and critically appraise existing research. 

This methodology utilises several legitimate techniques to shorten the process – careful focus of the research question, using broad or less sophisticated search strategies, conducting a review of reviews, restricting the amount of grey literature, extracting only key variables and performing more simple quality appraisals. 

Rapid reviews have an increased risk of potential bias due to their short timeframe. Documenting the methodology and highlighting its limitations is one way to mitigate bias. 

3. Narrative review

Also called a literature review.  

A narrative, or literature, review synthesises primary studies and explores this through description rather than statistics. Library support for literature review can be found in this guide . 

4. Meta-analysis

A meta-analysis statistically combines the results of quantitative studies to provide a more precise effect on the results. This type of study examines data from multiple studies, on the same subject, to determine trends.

5. Mixed methods/mixed studies

Refers to any combination of methods where one significant component is a literature review (usually systematic review). For example, a mixed methods study might include a systematic review accompanied by interviews or by a stakeholder consultation. 

Within a review context, mixed methods studies refers to a combination of review approaches. For example, combining quantitative with qualitative research or outcome with process studies. 

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What is a systematic review in research?

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A systematic review is a form of analysis that medical researchers carry out to synthesize all the available evidence on a particular question, such as how effective a drug is.

A meta-analysis is a type of systematic review. Instead of basing conclusions on a single study, a meta-analysis looks at numerous studies for the answer.

It pools numerical analyses from studies of similar design. A meta-analysis can also form part of a further systematic review.

A panel of experts usually leads the researchers who carry out a systematic review. There are set ways to search for and analyze the medical literature.

A systematic review is a high form of evidence. The conclusions help medical experts to form an agreement on the best form of treatment.

The findings also inform policies set by state healthcare systems, such as whether they should fund a new drug.

Conducting a systematic review

Scientists carry out medical research

The BMJ define a systematic review as “an overview of primary studies that used explicit and reproducible methods.”

Researchers carry out systematic reviews of all the available medical evidence and specifically of primary research. Primary research is data that researchers have collected from patients or populations.

Experts then base recommendations, or guidelines, on these findings. These guidelines lay out the treatment choices that health care providers and professionals should follow.

Researchers must carry out these reviews in a specific way, because they must ensure the recommendations that follow will result in the best healthcare for patients.

There are step-by-step instructions for conducting systematic reviews.

The Cochrane Library is a collection of systematic reviews that the international medical community respects. It follows a scientifically rigorous protocol to produce robust reviews.

The 2011 Cochrane Handbook for Systematic Reviews of Interventions lays out the guidelines that Cochrane require scientists to follow.

Producing a review: 8 steps

The Cochrane Library asks researchers to follow the steps below when producing a review. They provide a meticulous process through which researchers can synthesize data from a range of studies.

1: Define the research question

Researchers must first decide what research question they need an answer for. The aim could be, for example: “To assess the effects of a new drug for a particular health problem in certain types of people.” The question needs to be very specific.

2: Decide which studies to include in the review

The research question will partly decide this, but further “eligibility criteria” will define in advance which studies the team will include or exclude. The studies must have a rigorous design, for example, a randomized control trial (RCT) .

3: Search for the studies

Step 3 outlines which sources the researcher will consult and the search terms they will use to search for them. In a Cochrane review, specially trained search coordinators do this. The researchers should also try to identify unpublished studies.

4: Select the studies and collect the data

Researchers take data from studies that meet the predetermined eligibility criteria. The data may have to come from a variety of formats.

5: Assess the risk of bias in the included studies

This ensures that all the studies reviewed are relevant and reliable.

For example:

It is acceptable to include some studies of a lower quality, as long as the researchers take this kind of bias into account.

6: Analyze the data and undertake meta-analyses

This is the core process of a systematic review. It is the main step toward synthesizing conclusions. The previous steps must be complete before carrying out this step.

7: Address any publication bias

Publication bias is when researchers specifically choose, or cherry-pick, a study for inclusion. This can lead to a misrepresentation of the true effects of treatment.

Researchers should avoid cherry-picking and usually sign an agreement that they have no vested interest in the work. For instance, if they work for a pharmaceutical company and are supporting a drug made by that company they must disclose it.

8: Present the final results of the review

The team publishes the work, with a table showing a summary of findings. Decision makers can use this published outcome.

Advantages of a review

A systematic review is a synthesis or overview of all the available evidence about a particular medical research question. Based on the evidence currently available, it can give a definitive answer on a particular question about therapy, prevention, causes of disease, or harm.

The conclusions of a review are more reliable than those from a single study.

The BMJ list the following as key advantages of a systematic review:

It is helpful for establishing whether a certain technique or drug works and is safe.

A review can also:

Systematic reviews also offer practical advantages. They are less costly to carry out than a new set of experiments, and they take less time.


A systematic review may have some disadvantages.

Study design

It can be hard to combine the findings of different studies, because the researchers have carried out their investigation in different ways.

The number of participants, the length of the original study, and many other factors can make it hard to compare the findings of two or more studies.

Authors of a review must decide whether the quality of a source is “high” or “low,” in other words how reliable each one is. The decision usually depends the design of the study.

For instance, a randomized controlled trial is considered the highest of the primary studies. Other recommendations include transparency and reproducibility of judgments.

The role of unpublished research

If researchers only use published or readily available studies, it could be a threat to the validity of a review. This occurs because researchers tend to publish studies that show a significant effect and may not take the time to write up negative findings.

Unpublished studies can be hard to find, but using published literature alone may lead to misrepresentation because it does not include findings from all the existing research.

The term gray literature refers to articles or books not formally published and may include government reports, conference proceedings, graduate dissertations, unpublished clinical trials and more.

As previously mentioned, results that are negative or inconclusive, for example, may remain unpublished. Publication bias can cause positive results to become exaggerated, because the findings do not incorporate neutral or negative results.

Medical researchers are less likely to submit bad results, so systematic reviews could have a bias towards good results.

The role of editors and peer reviewers

The decisions of journal editors and peer reviewers can also lead to publication bias.

Sometimes, results do not reach the publication stage because there is funding for research, but this does not cover the cost of analyzing and publishing the results.

This can limit the motivation to write up and submit any negative or neutral findings for publication.

Standards for systematic reviews

In 2011, the Institute of Medicine (IOM) noted that systematic reviews can help clinicians make good decisions in their daily practice and help health organizations to prepare guidelines.

However, they added that systematic reviews can also be “uncertain or poor quality,” due to a lack of universal standards, especially when it comes to bias, conflicts of interest, and how authors evaluate evidence.

In an attempt to counter this, the IOM recommend some standards for authors to follow at each stage.

They provide guidelines for a number of areas, including:

What is a meta-analysis?

A meta-analysis uses a statistical approach to summarize the results of other studies, all of which must have a similar design. It aims to provide reliable evidence.

Using statistical analysis, researchers combine the numbers from previous studies, and they use this information to calculate an overall result.

The BMJ define a meta-analysis as “a mathematical synthesis of the results of two or more primary studies that addressed the same hypothesis in the same way.”

As with a review, authors must follow certain steps .

A meta-analysis can stand alone, or it can be part of a wider systematic review. A wider review can include results from studies of various scientific designs.

A meta-analysis can provide more reliable evidence than other investigations, but still the results may not always apply directly to the everyday treatment of disease.

Simple numerical answers cannot solve complex clinical problems, however, and they cannot tell a clinician how to treat a person.

A meta-analysis may also conclude, for example, that antibiotics are effective in treating a disease, but they are unlikely to specify the type, dosage, or how a specific antibiotic will affect an individual.

More studies and trials are necessary before healthcare providers can make these kinds of decision.

Medical research is crucial for understanding what works, what does not work, and whether a strategy or a drug is safe.

Systematic reviews and meta-analyses bring together the findings of several investigations. In theory, this makes the findings more reliable.

However, even this type of report has its pitfalls.

Whether they look at the findings of an investigation, a review, or a meta-analysis, healthcare professionals must always interpret the findings with care.

In the case of drugs and new medical techniques, clinical trials are necessary to get a better view of their safety and effectiveness.

Find out more about clinical trials from our article: How do clinical trials work?

Last medically reviewed on February 25, 2019

How we reviewed this article:

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A high-quality systematic review is described as the most reliable source of evidence to guide clinical practice. The purpose of a systematic review is to deliver a meticulous summary of all the available primary research in response to a research question. A systematic review uses all the existing research and is sometime called ‘secondary research’ (research on research). They are often required by research funders to establish the state of existing knowledge and are frequently used in guideline development. Systematic review findings are often used within the …

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Physical therapy in tension-type headache: a systematic review of randomized controlled trials.

systematic review article type

1. Introduction

2. materials and methods, 2.1. eligibility criteria, 2.2. information sources and search strategy, 2.3. study selection.

2.4. Data Collection Process

2.5. risk of bias in individual studies and summary measures, 3.1. study selection, 3.2. study characteristics and risk of bias within studies, 3.3. results of individual studies, 4. discussion.

5. Conclusions

6. limitations, author contributions, institutional review board statement, informed consent statement, data availability statement, conflicts of interest.

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Repiso-Guardeño, A.; Moreno-Morales, N.; Armenta-Pendón, M.A.; Rodríguez-Martínez, M.d.C.; Pino-Lozano, R.; Armenta-Peinado, J.A. Physical Therapy in Tension-Type Headache: A Systematic Review of Randomized Controlled Trials. Int. J. Environ. Res. Public Health 2023 , 20 , 4466. https://doi.org/10.3390/ijerph20054466

Repiso-Guardeño A, Moreno-Morales N, Armenta-Pendón MA, Rodríguez-Martínez MdC, Pino-Lozano R, Armenta-Peinado JA. Physical Therapy in Tension-Type Headache: A Systematic Review of Randomized Controlled Trials. International Journal of Environmental Research and Public Health . 2023; 20(5):4466. https://doi.org/10.3390/ijerph20054466

Repiso-Guardeño, Angela, Noelia Moreno-Morales, María Angeles Armenta-Pendón, María del Carmen Rodríguez-Martínez, Ricardo Pino-Lozano, and Juan Antonio Armenta-Peinado. 2023. "Physical Therapy in Tension-Type Headache: A Systematic Review of Randomized Controlled Trials" International Journal of Environmental Research and Public Health 20, no. 5: 4466. https://doi.org/10.3390/ijerph20054466

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Systematic review article, survival rate of colorectal cancer in china: a systematic review and meta-analysis.

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Background: This study aims to comprehensively summarize the colorectal survival rate in China. Method: In PubMed and Web of Science, keywords such as “colorectal cancer”, “survival” and “China” were used to search literatures in the past 10 years. Random effect models were selected to summarize 1-year, 3-year, and 5-year survival rates, and meta-regression and subgroup analyses were performed on the included studies.

Results: A total of 16 retrospective and prospective studies providing survival rates for colorectal cancer in China were included. The 1-year, 3-year, and 5-year survival rates of colorectal cancer in China were 0.79, 0.72 and 0.62, respectively. In the included studies, the 5-year survival rates of stage I (5474 cases), stage II (9215 cases), stage III (8048 cases), and stage IV (4199 cases) colorectal cancer patients were 0.85, 0.81, 0.57 and 0.30, respectively. Among them, the 5-year survival rates of colorectal cancer were 0.82, 0.76, 0.71, 0.67, 0.66, 0.65 and 0.63 in Tianjin, Beijing, Guangdong, Shandong, Liaoning, Zhejiang and Shanghai, respectively.

Conclusion: The 5-year survival rate in China is close to that of most European countries, but still lower than Japan and South Korea, and the gap is gradually narrowing. Region, stage, differentiation, pathological type, and surgical approach can affect 5-year survival in colorectal cancer.

Systematic review registration: https://www.crd.york.ac.uk/prospero/ identifier, CRD42022357789.

1. Introduction

Colorectal cancer (CRC) is the third most common cancer in the world. In 2020, there were 1.9 million new cases of CRC and 93,5000 related deaths ( 1 ) Currently, China is undergoing cancer transition with an increasing burden of gastrointestinal cancer. The incidences of CRC increased rapidly ( 2 ). In recent years, the economic burden associated with CRC has been rising. Studies have shown that CRC-related healthcare spending is growing rapidly, with overall direct healthcare expenditure per CRC patient in China exceeding GDP per capita in the same year ( 3 ). The proportion of rectal cancer in China decreased from 71.2% in the 1980s to 66.7% in the 1990s, while the proportion of colon cancer increased from 10.9% to 15.2% during the same period. In China, the incidence of left and right CRC is basically the same. Among all CRC patients, 49.2% are observed on the right side and 49.4% are observed on the left side. Adenocarcinoma remains the most common type of CRC ( 4 ).CRC-related genetic syndromes, such as Lynch syndrome and familial adenomatous polyposis are responsible for 5%−10% of all CRC cases ( 5 ). A retrospective study from China showed that Lynch syndrome is an autosomal dominant hereditary Disease, representing 4% of all CRC cases ( 6 ).

Survival rate is one of the most critical indicators to measure the therapeutic effect and prognosis of a certain disease. Many social factors will affect the survival of colorectal cancer patients, and the disease itself, such as stage, differentiation, pathological type, tumor site, inflammatory factor, age and gender, will also affect survival ( 7 ). The 5-year survival rate of patients with stage I colon cancer was as high as 96.6%, while the 5-year survival rate of patients with stage IV colon cancer was only 34.3% ( 8 ). Research has reported that younger patients have a worse prognosis than older patients ( 9 ). A single-institution retrospective study showed better survival after radical resection of left colon cancer than right colon cancer, with a significant difference in 5-year overall survival between right and left colon cancer (82.1% vs . 88.7%, P < 0.05) ( 10 ). In the past few decades, the survival rate of CRC patients has improved significantly with the improvement of diagnostic technology and treatment, but there are still significant regional differences in the survival rate of CRC patients across the country.

There are many researches on the survival rate of CRC in China, providing valuable experience for the treatment and prognosis by understanding the survival rate of colorectal cancer in different regions and at different times. The purpose of this study is to analyze and summarize the survival rate of CRC in China.

2. Materials and methods

2.1. study design.

This systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). By applying the Problem/Population, Intervention, Comparison, and Outcome (PICO) framework, the patients involved in our meta-analysis were colorectal cancer patients. We do not have a specific definition of “Intervention”. Articles that provided survival were included. In all included studies, the “Comparison” element of the PICO framework was not involved because we performed a pooling of single-group rates. The primary outcomes were 1-year, 3-year, and 5-year survival rates.

2.2. Search strategy

This systematic review and meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) statements checklist. A comprehensive, computerized literature search was conducted in PubMed and Web of Science for relevant studies between January 2011 and December 2021. The keywords and MeSH terms we used for retrieval were: (colorectal) or (colon) or (rectum) and (Neoplasms) or (tumor) or (cancer) or (Malignancy) or (carcinoma) and (survival) or (survival rate) or (survival analysis) or (prognosis) and (China). The search strategy was repeatedly performed until no new relevant articles were found. In addition, we reviewed references in the retrieved articles to search for additional relevant studies. All articles were evaluated by two authors based on the eligibility criteria we designed.

2.3. Selection of researches

First, we checked titles and abstracts of articles that were searched by using keywords to exclude irrelevant articles. Then the retrieved literatures were imported into “EndNote X9” software to exclude the duplicated ones before being screened by two reviewers independently. The exclusion criteria for our studies were as follows. (1) Studies were published in the year before 2011. (2) Articles that do not accurately provide complete survival information. (3) Studies with a sample size of less than 500 patients. (4) Article type is meta-analysis or review. (5) The language of the article is non-English.

2.4. Quality evaluation and data extraction

We evaluated comparative studies using the Newcastle-Ottawa Quality Assessment Scale for Cohort Studies. For the methodological quality evaluation of randomized controlled trials, we took reference to the Cochrane Handbook for Systematic Reviews of Interventions. Data were extracted independently by two researchers and any discrepancies in the data were settled by consensus. If necessary, a third researcher was expected to participate in the discussion and make a decision.

Data were extracted independently by two researchers using pre-designed standard forms, including corresponding author, study design, publication year, research year, region of patients, number of patients, age, sex, tumor site, tumor stage, differentiation, pathological type, surgical approach and 1-, 3- and 5-year survival rates. All data were extracted directly from the original text or calculated from the data known in the original text.

2.5. Data analysis

Firstly, we generated combined 1-, 3- and 5-year survival rates. Second, we performed subgroup analysis and meta-regression analysis when heterogeneity existed between the studies. Subgroup analysis was performed based on the factors of study region, stage, differentiation, pathological type, surgical approach, age and gender. The 5-year survival rates of different subgroups were calculated. The factors of sample size, publication year, research year and study region were included into the meta-regression model for meta-regression analysis. Sensitivity analysis was performed to investigate the risk of publication bias for individual studies. Finally, Egger bias test and funnel plot were used to evaluate the risk of publication bias in the included researches. We used Stata13 for meta-analysis and Graphpad for mapping.

3.1. Included researches and their characteristics

Sixteen researches were eventually included in the meta-analysis ( 11 – 26 ). The combined search identified 837 literatures published, of which 309 duplicates were excluded. 483 were rejected based on the title and abstract evaluation (402 articles did not mention survival rate, 46 articles were meta-analyses and reviews, and 35 articles were non-English), and the remaining 45 articles underwent full-text evaluation. In order to minimize publication bias and make the included researches more representative, we excluded 25 researches with the number of cases fewer than 500. Three researches ( 13 , 27 , 28 ) were proven to be based on the same patient population, so only the one with the most comprehensive information was included ( 13 ). There were two researches ( 26 , 29 ) with the same situation, and we excluded the one with less comprehensive information ( 29 ). One epidemiological research was excluded because it was unable to calculate overall survival rate of CRC patients. A flow diagram of the literature selection process used in this study was shown in Figure 1 . The 16 researches with 62,748 patients, including 4 from Shanghai, 2 each from Zhejiang and Shandong provinces, and 1 each from Guangdong, Anhui and Jiangsu provinces, Tianjin, Beijing and Xinjiang. Table 1 summarizes the features of the included researches.


Figure 1 Flowchart of Search and Studies Selection.


Table 1 Characteristics of Included Studies.

3.2. Survival rate

The median follow-up of the 16 researches was 19.76 to 130 months. Four researches mentioned 1-year survival rate of 27363 patients; eight researches included information on 3-year survival rate of 42,165 patients; sixteen researches provided enough data to calculate 5-year survival rates. The 1-, 3- and 5-year survival rates of Chinese CRC patients summarized by the random-effect model were 0.79 (95%CI: 0.63-0.94), 0.72 (95%CI: 0.64-0.79) and 0.62 (95%CI: 0.54-0.70) respectively ( Figure 2 ).


Figure 2 Pooled survival rate. (A) Forest plot of pooled 1-year survival rate in patients with colorectal cancer. (B) Forest plot of pooled 3-year survival rate in patients with colorectal cancer. (C) Forest plot of pooled 5-year survival rate in patients with colorectal cancer. (D) Histogram of pooled 1, 3, 5-year survival rate in patients with colorectal cancer.

3.3. Subgroup analysis

In order to reduce heterogeneity and more deeply compare the impact of patient characteristics on survival rate, we performed the subgroup analysis. The results showed significant differences in 5-year survival rates among CRC patients in different regions. Based on regional subgroup analysis, Tianjin had the highest 5-year survival rate (0.82), followed by Beijing (0.76), Guangdong (0.71), Shandong (0.67), Liaoning (0.66), Zhejiang (0.65), Shanghai (0.63), and Xinjiang had the lowest 5-year survival rate (0.26, 95%CI:0.24-0.29) ( Figure 3 ). The subgroup analysis of different stages of the cancer showed that the 5-year survival rate at stage I was 0.85 (95%CI:0.80-0.90), at stage II was 0.81 (95%CI:0.78-0.85), at stage III was 0.57 (95%CI:0.49-0.65), and at stage IV was only 0.30 (95%CI:0.15-0.46) ( Figure 4A ). Four researches directly compared 5-year survival rates among patients with different degrees of differentiation, with 5-year survival rates of 0.77 (95%CI: 0.70-0.85) and 0.72 (95%CI: 0.68 -0.77) in the highly and moderately differentiated subgroups respectively, and 0.57 (95%CI: 0.49 - 0.65) in the poorly differentiated subgroup ( Figure 4B ). In addition, according to the subgroup analysis based on different pathological types of the tumor, the 5-year survival rate was 0.68 (95%CI:0.63-0.73) in the adenocarcinoma subgroup and 0.55 (95%CI: 0.52-0.59) in the mucinous adenocarcinoma subgroup ( Figure 4C ). The 5-year survival rate of radical surgery patients in our study was 0.73(95%CI:0.71-0.76), while the 5-year survival rate of palliative surgery patients was only 0.15(95%CI:0.09-0.22) ( Figure 4D ). The histogram summarizes the 5-year survival rate of patients in subgroups with different tumor stage, differentiation, pathological type, surgical approach ( Figure 4E ). There were no significant differences in subgroup analysis based on age, sex, and tumor site, as shown in Supplementary Figure 1 and Supplementary Figure 2 .


Figure 3 Survival rates in different regions (A) Forest plot of survival rates in different regions. (B) Histogram of survival rates in different regions.


Figure 4 Subgroup analysis. (A) Forest plot of subgroup analysis based on stage. (B) Forest plot of subgroup analysis based on differentiation. (C) Forest plot of subgroup analysis based on pathological type. (D) Forest plot of subgroup analysis based on surgical method. (E) Histogram of subgroup analysis based on stage, differentiation, pathological type and surgical method. AC, Adenocarcinoma; MAC, Mucinous adenocarcinoma.

3.4. Meta-regression analysis

We performed the meta-regression analysis to explore the potential causes of heterogeneity, fitting factors of sample size, publication year, research year and study region into a univariate model. The results showed that sample size and study region were the main causes for heterogeneity, with P values of 0.001 and 0.000 respectively. Meta-regression analysis based on publication year and hospitalization year of the patients found no significant heterogeneity, with P values of 0.075 and 0.437 ( Table S1 , Supplementary Figure 4 ).

3.5. Publication bias and evaluation of reference quality

In the evaluation of publication bias in the included studies, we found asymmetry in funnel plot ( Supplementary Figure 4 ), however, it was proven in the more sensitive Egger test that publication bias of the included researches did not exist ( P =0.508) ( Figure 5A ). Sensitivity analysis showed that there was rather significant heterogeneity in the researches from Guoqing Zhang’s research group and Jianguo Chen’s research group ( 11 , 15 ) ( Figure 5B ). We believe that heterogeneity may be due to differences in regions and publication years of the study. The economic development, medical level, lifestyle and dietary habits differs from regions, and might affect survival rates in CRC patients. As for Chen’s study, the diagnosis year for the included patients is 1993-2007, which may lead to publication bias. After experiencing regional economic development, improvement of comprehensive treatment options, and changes in healthcare and services, CRC survival rates vary from different years. However, this article can truly reflect the prognosis of CRC patients in China over the past 50 years. We then assessed the methodological quality of all included researches. In one randomized controlled trial, Cochrane Handbook for Systematic Reviews of Interventions alone was used to evaluate its methodological quality, and the risk was evaluated as low for all parts. One epidemiological research ( 15 ) provided effective survival rates for the meta-analysis, but there was not enough information for the evaluation of methodological quality, so the rate was rather low (4 stars), while the quality of rest of the researches were all equal to or higher than 5 stars ( Table S1 ).


Figure 5 Egger’s publication bias plot and sensitivity analysis. (A) Egger’s publication bias plot based on 5-year survival rate. (B) Sensitivity analysis based on 5-year survival rate. Every horizontal line representing combined 5-year survival and the range of 95% CI after omitting study of the included studies one by one.

4. Discussion

The 1-, 3- and 5-year survival rates of patients with CRC in China were obtained in this meta-analysis. Among the included studies, the pooled 1-year and 3-year survival rates were 0.79 (95%CI: 0.63-0.94) and 0.72 (95%CI: 0.64-0.79), respectively. According to a population-based data analysis, the 1-year survival rates of patients with CRC in Australia, Canada, Norway, Denmark, and the United Kingdom were 0.849, 0.835, 0.824, 0.777, and 0.747, respectively ( 30 ). The 1-year survival rates in these regions were basically consistent with our findings. The pooled 5-year survival rate of the 16 included studies was 0.62 (95% CI: 0.54-0.70). A study published in 2019 reported 5-year survival rates for CRC patients in Australia, Canada, Denmark, Ireland, New Zealand, Norway and the United Kingdom. The highest survival rate was 0.708 (95%CI: 0.70-0.715) in Australia, and the lowest was 0.589 (95%CI: 0.586-0.593) in The UK ( 31 ). The 5-year survival rate of CRC in China was close to most European countries. Comparatively, Japan, an Asian country, has a 5-year survival rate of 0.73 for CRC, 0.628 for South Korea; 0.61 for Iran; 0.582 for Jordan and 0.342 for Malaysia ( 32 – 36 ). The 5-year survival rate in China was still lower than Japan and South Korea, but the gap was gradually narrowing.

Many factors can affect the prognosis of CRC patients, such as economic status, cancer stage, histological type, tumor location, and age at diagnosis ( 37 , 38 ). The incidence and mortality of CRC in regions with high Human Development Index (HDI) in the world are at least twice as high as those in regions with low HDI ( 39 ). We found that region had an effect on 5-year survival. CRC is a multifactorial disease caused by lifestyle, genetic and environmental factors ( 40 – 42 ). China has a wide geographical area, and different regions have different lifestyles and dietary habits, which lead to different survival rates of CRC in different regions. A study from Malaysian also confirmed wide regional differences in CRC survival ( 43 ). In our research, Tianjin had the highest 5-year survival rate (0.82, 95%CI: 0.79-0.85), and Xinjiang had the lowest 5-year survival rate (0.26, 95%CI:0.24-0.29). Due to the small number of included studies, only one study mentioned the 5-year survival rate in Xinjiang (0.26), so it cannot comprehensively represent the 5-year survival rate of patients with CRC in the entire Xinjiang region. The high 5-year survival rate in Tianjin was also due to the fact that the study targeted at stage I CRC patients. For CRC, screening is conducive to early diagnosis and can improve the survival rate of CRC patients. Thus, CRC screening has been recommended in clinical practice guidelines in many countries ( 44 , 45 ). The implementation of the National Danish Colorectal Cancer Screening Programme was considered a success and the programme was hopefully in the process of reducing colorectal cancer morbidity and mortality in Denmark ( 46 ). Policies vary from region to region, and some cities have cancer screening programs in place. For example, in Shanghai, as early as 2013, the CRC screening program was incorporated into community medical services, which greatly improved the 5-year survival rate of patients with colorectal cancer in Shanghai ( 20 ).

The pathological stage of tumor at the initial diagnosis is the most important factor in determining the behavior and prognosis for CRC, and mortality rises with tumor stage ( 47 , 48 ). In our study, the pooled 5-year survival rate at stage I was 0.85, 0.81 at stage II, 0.57 at stage III, and 0.30 at stage IV. It is difficult for patients at stage III and IV to achieve radical cure of the disease and reduce the survival rate. Due to the deeper tumor infiltration, the cancer cells involve surrounding tissues, organs and regional lymph nodes. Rajaa Chatila’s study also confirmed that stage was a major determinant of prognosis in patients with CRC. After adjusting for age and gender in his study, there was a highly significant difference between stage IV patients and stage I patients (HR = 8.81, 95% CI: 3.20-24.22, p = 0.000) ( 49 ). Incorporating the surgical method (radical or palliative) into the nomogram model can visually display that the surgical method was an independent prognostic factor affecting the overall survival rate of CRC patients ( 50 ). Therefore, the 5-year survival rate of radical surgery patients in our study was 0.73, while the 5-year survival rate of palliative surgery patients was only 0.15. In the subgroup analysis, the 5-year survival rate of the well-differentiated subgroup was 0.77, the 5-year survival rate of the moderately differentiated subgroup was 0.72, and the 5-year survival rate of the poorly differentiated subgroup was 0.57. The existence of prognostic differences between mucinous and non-mucinous colorectal carcinoma, mucinous differentiation results in increased hazard of death ( 51 ). In our results, the 5-year survival rates for adenocarcinoma and mucinous adenocarcinoma were 0.68 and 0.55, respectively. Mucinous adenocarcinoma showed a lower 5-year survival rate. The reason may be that mucinous adenocarcinoma, a pathological type, has different characteristics from adenocarcinoma, including younger patients, an advanced stage at diagnosis, and more prone to metastasis ( 52 ).

The results of subgroup analysis showed that there was no significant difference in the 5-year survival rate with different age, gender, and tumor site. The 5-year survival rates of patients <60 years and ≥60 years were 0.70 and 0.67, while 0.67 and 0.70 in male and female, respectively. Primary tumor site affects prognosis in patients with CRC. Although there have been studies reporting that right-sided colon cancer has worse overall survival compared to left-sided colon cancer, in our study, there was no significant difference between the two (0.74 vs . 0.71) ( 53 – 57 ). The 5-year survival rates of colon and rectal cancer subgroups were almost equal (0.70 vs . 0.69). It may be related to the fact that we included too few studies, with only 6 studies summarizing 5-year survival in patients with colon/rectal cancer and only 3 studies comparing 5-year survival in the left colon versus the right colon.

One of the limitations of this study is that although we included up to 62748 patients, the number of studies included was small. In order to minimize publication bias and make the included researches more representative, we chose to include researches from large study centers. We determined a threshold of 500 cases based on the actual number of patients in the articles. We hope that this threshold can reduce bias. Many studies did not mention 1-year and 3-year survival, resulting in only 4 studies summarizing 1-year survival and 8 studies summarizing 3-year survival. The information about the survival rate in many studies was not comprehensive. We obtained the survival rate by calculation, so there may be minor deviations. Lynch syndrome is a common CRC-related genetic syndrome. Unfortunately, available research data could not support comparisons of survival rates for genetic and non-hereditary colorectal cancers. The vast majority of Chinese cities have not published studies on CRC survival rates, so it was impossible to summarize the survival rates in various regions of China. Moreover, there were too few related studies in some areas, which is prone to the phenomenon of generalization like the 5-year survival rate in Xinjiang. Summarized information on survival rates of CRC patients in China is lacking. Our study complements the 5-year survival rate information for CRC in different regions and different clinicopathological features in China.

5. Conclusions

The 5-year survival rate in China is close to that of most European countries, but still lower than Japan and South Korea, and the gap is gradually narrowing. Region, stage, differentiation, pathological type, and surgical approach can affect 5-year survival in colorectal cancer.

Data availability statement

The original contributions presented in the study are included in the article/ Supplementary Material . Further inquiries can be directed to the corresponding author.

Author contributions

HL and JL contributed to the research concept and design. RW and XW retrieved and filtered articles, and XP and BX extracted data. RW and JL analyzed the data. RW, XW, JS, and ST explained the data. RW and JL drafted manuscript. HL and JL contributed to critical revision of the manuscript. All authors contributed to the article and approved the submitted version.

This research was funded by the National Natural Science Foundation of China (grant nos. U20A20376 and 61972116), Beijing Award Foundation (YXJL-2020-0818-0478), Wu Jieping Medical Foundation (320.6750.2020-19-20), Heilongjiang Province Postdoctoral Science Foundation (LBHZ21189), Harbin Medical University Innovative Science Research Funded Project (grant no.2022-KYYWF-0289) and China Postdoctoral Science Foundation (grant no.2022MD713747).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fonc.2023.1033154/full#supplementary-material

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Keywords: colorectal cancer, overall survival, meta-analysis, China, epidemiology

Citation: Wang R, Lian J, Wang X, Pang X, Xu B, Tang S, Shao J and Lu H (2023) Survival rate of colorectal cancer in China: A systematic review and meta-analysis. Front. Oncol. 13:1033154. doi: 10.3389/fonc.2023.1033154

Received: 31 August 2022; Accepted: 20 February 2023; Published: 03 March 2023.

Reviewed by:

Copyright © 2023 Wang, Lian, Wang, Pang, Xu, Tang, Shao and Lu. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY) . The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

*Correspondence: Haibo Lu, [email protected]

† These authors have contributed equally to this work

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European Journal of Vascular and Endovascular Surgery

Systematic review optimal timing of thoracic endovascular aortic repair for uncomplicated type b aortic dissections: a systematic review and meta-analysis.

Type B aortic dissections (TBAD) have a high mortality and are challenging to both classify and manage. There is significant evidence supporting the use of early intervention in complicated TBAD with thoracic endovascular aortic repair (TEVAR). Currently, there is equipoise regarding the optimal timing for TEVAR in TBAD. This systematic review answers whether early TEVAR in the hyperacute/acute phase of the disease has improved aorta related events in the one year follow up period with no change in mortality when compared with TEVAR in the subacute/chronic phase.

Data sources

A systematic review and meta-analysis was performed with Preferred Reporting Items for Systematic Reviews and Meta-Analyses literature search guidelines for MEDLINE, Embase, and Cochrane Reviews until 12 April 2021. Inclusion and exclusion criteria targeting the review objective and high quality research were employed by separate authors.

Review methods

These studies were then reviewed for suitability, risk of bias, and heterogeneity using the ROBINS-I tool. Results were extracted for the meta-analysis with RevMan using odds ratios with 95% confidence intervals with I 2 used to assess heterogeneity.

A total of 20 articles were included. A meta-analysis showed no significant difference between acute phase TEVAR (excluding the hyperacute phase) and subacute/chronic phase TEVAR for all cause 30 day and one year mortality. Aorta related events in the 30 day post-operative period were unaffected by the timing of intervention but had significant improvement in aorta related events in the one year follow up favouring TEVAR in the acute phase compared with subacute/chronic phase. Risk of confounding was high but with low heterogeneity.

Without prospective randomised controlled studies, it is evident that there is improved aortic remodelling in long term follow up with intervention in the acute setting from three to 14 days after symptom onset. This suggests that TEVAR in the acute period of TBAD is both safe and beneficial, and can be considered for early stent grafting based on clinical, anatomical and patient factors.

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This meta-analysis suggests that treating type B dissections with thoracic endovascular aortic repair (TEVAR) in the acute period (2 – 14 days) improves one year aorta related events with no statistically significant difference in mortality in the 30 day post-operative period or one year follow up. Early treatment of type B dissections may have improved aortic remodelling favouring long term aorta related outcomes without significantly affecting short or long term mortality. There is likely a subgroup of patients with uncomplicated type B dissections who would benefit from early intervention with TEVAR.

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Open Access

Study Protocol

Safety and efficacy of anti-hyperglycemic agents in patients with type 2 diabetes mellitus (T2DM): Protocol for an overview of systematic reviews based on network meta-analysis

Contributed equally to this work with: Zhengping Chang, Jianguo Xu

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Project administration, Software, Writing – original draft, Writing – review & editing

Affiliation Department of General Medicine, Pingliang Rehabilitation Center Hospital, Pingliang, China

Roles Conceptualization, Formal analysis, Investigation, Methodology, Software, Writing – original draft, Writing – review & editing

Affiliation Evidence-Based Medicine Center, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China

Roles Data curation, Formal analysis, Methodology, Software, Writing – review & editing

Roles Data curation, Formal analysis, Methodology, Resources, Writing – review & editing

Affiliation Evidence-Based Nursing Center, School of Nursing, Lanzhou University, Lanzhou, China

Roles Formal analysis, Funding acquisition, Methodology, Software, Writing – review & editing

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Software, Writing – original draft, Writing – review & editing

Affiliation Department of Endocrinology, Gansu Provincial Hospital, Lanzhou, China

Roles Conceptualization, Methodology, Project administration, Supervision, Validation, Writing – review & editing

* E-mail: [email protected]

Affiliation Department of Spinal Cord Injury Rehabilitation, Gansu Province Hospital Rehabilitation Center, Lanzhou, China

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Table 1

Type 2 diabetes mellitus (T2DM) has caused a huge clinical and economic burden worldwide. The management strategy of T2DM has been mentioned in many guidelines. However, controversy still exists in the recommendation of anti-hyperglycemic agents. To this end, this protocol has been written according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P). We will make an overview of systematic reviews based-on network meta-analysis firstly that report on safety and efficacy of different category of anti-hyperglycemic agents for T2DM patients. We will identify network meta-analysis by applying a robust and standardized search strategy within Embase, PubMed, Web of Science, and Cochrane Database of Systematic Reviews. Hemoglobin A1c (HbA1c) and fasting plasma glucose (FPG) will be defined as the primary outcomes. We will assess the methodological quality of included reviews by applying the A MeaSurement Tool to Assess Systematic Reviews (AMSTAR-2) tool, and quality of evidence for all outcomes will be judged by using the Grading of Recommendations Assessment, Development and Evaluation (GRADE). This will provide an accessible narrative synthesis to clinicians, patients, policy makers, and developers of clinical guidelines based on published high-quality network meta-analysis. We will submit our results for peer-review publication and presentation at domestic and international conferences. We will also disseminate our results through established clinical networks and consumer networks, using pamphlet where appropriate. Ethics approval is not required for this overview as we will analysis published network meta-analysis only.

Trial registration number: INPLASY202070118 .

Citation: Chang Z, Xu J, Qin Y, Zheng Q, Zhao L, Wang Y, et al. (2023) Safety and efficacy of anti-hyperglycemic agents in patients with type 2 diabetes mellitus (T2DM): Protocol for an overview of systematic reviews based on network meta-analysis. PLoS ONE 18(3): e0282143. https://doi.org/10.1371/journal.pone.0282143

Editor: Temesgen Muche Ewunie, Dilla University, ETHIOPIA

Received: June 25, 2021; Accepted: February 9, 2023; Published: March 3, 2023

Copyright: © 2023 Chang et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: No datasets were generated or analysed during the current study. All relevant data from this study will be made available upon study completion.

Funding: This study was supported by the Lanzhou Talent Innovation and Entrepreneurship Project in the form of a grant (2020-RC-63) awarded to YZ. No additional external funding was received for this study. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Abbreviations: T2DM, Type 2 diabetes mellitus; IDF, International Diabetes Federation; INPLASY, International Platform of Registered Systematic Review and Meta-analysis Protocols; TZDs, thiazolidinediones; ACDs, active comparator drugs; DPP-4 inhibitors, dipeptidyl peptidase-4 inhibitors; GLP-1, Glucagon-like peptide-1; SGLT-2 inhibitors, sodium/glucose cotransporter 2 inhibitors; HbA1c, hemoglobin A1c; FPG, fasting plasma glucose; 2HPPG, 2 h postprandial blood glucose; BMI, body mass index; URTI, upper respiratory tract infection; HR, hypersensitivity reaction; PICOS, Participants, Intervention, Control, Outcome, Study design; GRADE, Grading of Recommendations Assessment, Development and Evaluation; AMSTAR, A MeaSurement Tool to Assess Systematic Reviews; PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses

1. Introduction

Diabetes is a chronic and progressive disease featured by the deterioration in blood glucose control over time. It has caused significant clinical and economic burdens worldwide [ 1 ]. Twenty years ago, an estimated 151 million adults worldwide had diabetes. A decade ago, in 2010, the incidence of diabetes increased by 88% to 285 million, and now this data is 463 million [ 2 , 3 ]. If adequate action is not taken to address the pandemic, The International Diabetes Federation (IDF) estimates that there will be 578 million adults with diabetes by 2030, and 700 million by 2045 [ 3 ]. In 2019, the worldwide total diabetes-related healthcare expenditure for adults aged 20–79 are estimated to be USD 760 billion, of which the majority (68.7%) are those aged 50–79 years. It is estimated that by 2030, related healthcare expenditure will grow to USD 825 billion [ 3 , 4 ].

Type 2 diabetes mellitus (T2DM) is the most common type of diabetes, accounting for approximately 90% of diabetes worldwide. Globally, the prevalence of T2DM is estimated at 9% in the adult population, and it is rising across all regions [ 5 , 6 ]. This rise is driven by an aging population, economic development, and growing urbanization. The foundation of T2DM management is to maintain a healthy lifestyle and an appropriate body weight [ 7 ]. If trying to change lifestyle is not enough to control blood glucose levels, current guidelines [ 8 ] recommend metformin as the first-line agent for the treatment of T2DM with insufficient diet and exercise. When metformin monotherapy cannot be tolerated or contraindicated, or the efficacy is insufficient to control hemoglobin A1c (HbA1c) to achieve the desired target, the second anti-hyperglycemic agent is recommended as an alternative or additional therapy [ 9 , 10 ]. When oral medications are unable to control hyperglycemia to recommended levels, insulin therapies may be necessary [ 11 ]. However, the recommendations of different guidelines [ 8 – 10 , 12 , 13 ] regarding the selection of second-line agents are also controversial. Risk stratification management and therapeutic regimens optimization of T2DM patients need high-quality evidence to support it.

In 2011, the Ann Intern Med published the first network meta-analysis [ 14 ] on the comparative effectiveness of glucose-lowering drugs for T2DM. In the following ten years, many similar network meta-analysis appeared in this domain, comparing the safety and efficacy of different combination, dosage, course of treatment, and frequency of medication on T2DM between different anti-hyperglycemic drugs [ 15 – 18 ]. This overview will formally assess the quality of methodology and evidence of existing network meta-analysis in this domain.

Specifically, the objectives we aim to access include: 1) make a narrative synthesis of the evidence to get an insight for different agent therapy strategy for T2DM, and 2) make an evidence map based on Grading of Recommendations Assessment, Development and Evaluation (GRADE) to guide the use of anti-hyperglycemic agents. To this end, the proposed overview of systematic reviews will answer the following questions: 1) What is the methodological quality of published network analysis in this field? 2) What are the efficacy and safety of various anti-hyperglycemic agents verified by systematic review based on network meta-analysis and which agents are suitable for patients with different risk stratification? 3) Based on GRADE hierarchy of evidence, what are the strength of evidence and recommendation level of the various agents included in the network meta-analysis?

2. Materials and methods

2.1. protocol and registration.

In accordance with the guidelines, the protocol for this overview of systematic reviews was reported with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015 checklist [ 19 , 20 ]. It was registered with the International Platform of Registered Systematic Review and Meta-analysis Protocols (INPLASY) [ 21 ] on 27 July 2020 and was last updated on 5 August 2022 (registration number INPLASY202070118). Available in full on the inplasy.com ( https://doi.org/10.37766/inplasy2020.7.0118 ).

2.2. Eligibility criteria

Studies will be selected based on the criteria listed below to identify multiple systematic reviews on related research questions in the same topic area [ 22 ]. If the research protocol in PICOS is revised, the date of each amendment about eligibility criteria will be accompanied by an explanation of the changes and reasons.

2.2.1. Study designs.

We will include peer-reviewed and published network meta-analysis of anti-hyperglycemic agents for T2DM which provide meta-estimates for outcomes. Both direct comparison and indirect comparison of network meta-analysis will be included. The network meta-analysis that is ongoing or published in the form of conference abstracts will not be included.

2.2.2. Participants.

We will limit our overview of systematic reviews to studies of adults with T2DM, regardless of gender, race, or the presence of insulin resistance. The pregnant women with gestational diabetes will be excluded.

2.2.3. Interventions/Comparators.

Comparisons among the following interventions were included: insulin, metformin, sulfonylureas, thiazolidinediones (TZDs), active comparator drugs (ACDs), dipeptidyl peptidase-4 (DPP-4) inhibitors, Glucagon-like peptide-1 (GLP-1) analogues or agonists, sodium/glucose cotransporter 2 (SGLT-2) inhibitors, α-glucosidase inhibitors, meglitinides, or placebo. There are no restrictions on the combination formula such as whether to plus other agents to metformin or sulfonylureas. There are also no restrictions on different doses or frequency of the same agent. We classify all eligible drugs according to the above drug categories and because different drugs in the same category may have a variable effect, we include studies that compare drugs in a same category either. If a network meta-analysis included drugs of interest but also included drugs that were not of interest, or if multiple interventions included glycemic control by non-pharmacological methods, such studies would also be included. Interventions includes some drugs but not any drugs of interest within the list except for comparator drugs will not be included.

2.2.4. Outcomes.

The primary outcomes are HbA1c and fasting plasma glucose (FPG). The second outcomes are body mass index (BMI), 2 h postprandial blood glucose (2HPPG), body weight and adverse events, including hypoglycemia, diarrhea, upper respiratory tract infection (URTI), hypersensitivity reaction (HR), cardiovascular outcomes, renal and hepatic toxicity [ 23 , 24 ]. The second outcomes will be adjusted according to the final inclusion of the literature.

2.2.5. Language.

No restrictions will be placed on the original languages to which the literature will be included. Languages other than English and Chinese will be processed with the help of translation software tools or by seeking native speakers.

2.3. Information sources and search strategy

Our overview will search for systematic reviews including network meta-analysis from the following databases: PubMed, Embase, Web of Science, and Cochrane Database of Systematic Reviews. Search terms include diabetes and network meta-analysis . A researcher from evidence-based medicine center will create and run a search string to identify relevant articles. Take electronic databases PubMed which planned to be searched as an example, the pre-search strategy is presented in Table 1 . The search strategy will undergo internal peer review. The research is expected to officially start in December 2022.



2.4. Study records

2.4.1. data management..

The retrieved articles from the databases were exported to EndNote X9 for duplicate removal and further categorization. The full text of eligible reviews will also be attached to EndNote X9.

2.4.2. Network meta-analysis selection and data collection.

We will follow the recommendations in the Cochrane handbook for quality control and transparency of independent screening [ 25 ]. Two authors (one is a physician in the Department of Endocrinology, and the other is a researcher from the Evidence-Based Medicine Center) will independently screen the titles and abstracts, than to determine the preliminary inclusion of systematic reviews according to the eligibility criteria. While insufficient data are available or where there is any uncertainty in the abstract, the full-text will be retrieved. Any differences in selection will be resolved through discussion to reach a consensus or by adjudicating with a third author. We will record the excluded articles and the reasons for their exclusion. If necessary, we will get additional information for unclear or doubtful data from the corresponding authors by email. We shall use Microsoft Excel to perform pre-development spreadsheets to extract data of each review. The third author will check the data extracted by the two reviewers, and finally reach a consensus on the inconsistent data through discussion.

2.5. Data items

The reviewers will extract the following data items from each included systematic review: 1) Bibliographic details (author, institution, publication year, journal, country, funding). 2) Methodological characteristics (search end date, study design of primary research, agent and dose, length of duration of treatment, funding). 3) Method of pooling and bias assessment (homogeneity assumptions, similarity assumptions, and consistency assumptions in network meta-analysis, the choice of frequency and Bayesian methods in statistics, and the choice of statistical software for analysis to refine our study, risk of bias assessment tool). 4) Patient characteristics (age, gender, race, the therapeutic effect of first-line drugs). 5) Results (number of studies included in meta-estimate, event rate in different arms or patient populations, meta-estimate, risk of bias within included studies, risk of bias in meta-estimate).

2.6. Risk of bias individual studies

2.6.1. assessment of methodological quality of included reviews..

Two reviewers will independently assess the methodological quality of included network meta-analysis using A MeaSurement Tool to Assess Systematic Reviews (AMSTAR-2) tool [ 26 ]. The AMSTAR-2 has 16-domains covering topics including review registration, comprehensiveness of the literature search, inclusion/exclusion strategy, critical appraisal/results synthesis, and risk of bias (e.g., assessment and publication bias). Each domain is rated ‘yes’, ‘partial yes’, or ‘no’, and the overall quality of the study will be rated as ‘high’, ‘moderate’, ‘low’, or ‘critically low’ [ 27 ]. Any differences between author assessments will be resolved by discussion or adjudication by a third author. We will not exclude any reviews from the overview based on the results of this assessment.

2.6.2. Assessment of quality of evidence.

The quality of evidence for all outcomes will be judged using GRADE systems [ 28 , 29 ]. This tool has been previously selected and applied to improve the transparency and consistency in quality assessments of overview of systematic reviews [ 30 , 31 ]. The quality of evidence will be assessed across the domains of risk of bias, consistency, directness, precision, and publication bias. Quality will be adjudicated as high, moderate, low, or very low. Two principles of the original GRADE NMA guidelines are that we need to rate the certainty of each pairwise comparison of evidence within the network individually, and that in doing so we need to consider both direct and indirect evidence [ 32 ]. We follow the GRADE group’s recommendations for assessing the certainty of evidence: (1) it is not necessary to consider imprecision when rating direct and indirect estimates in order to inform the rating of NMA estimates; (2) it is not necessary to rate indirect evidence when the certainty of the direct evidence is high and the contribution of the direct evidence to the network estimates is at least as large as the contribution of the indirect evidence. (3) we should not trust statistical tests of the overall inconsistency of the network to assess inconsistency at the pairwise comparison level, and (4) where there is inconsistency between direct and indirect evidence, the certainty of the evidence for each estimate can help in deciding which estimate to trust.

The strict criteria on which we will base our synthesis will ensure that only those systematic reviews based on network meta-analysis with a high quality contribute to the evidence [ 33 ]. Disagreements over the assessment of the quality of evidence will be resolved by discussion with a third author.

2.7. Data synthesis

We will consider the issue of overlapping primary studies prior to preparing our evidence synthesis. If there are multiple network meta-analysis that include the same agents in the same patient, and measure the same outcome, we will deal with overlapping primary documents by the following methods: 1) If the primary research completely overlaps (repetition rate ≥ 80% of any one of the article), then we will choose the highest quality review.2) If the primary studies partially overlap, and the repetition rate is between 50% and 80%, then we will retain both reviews if the lower-quality review consists of more than 30% new studies. 3) If the primary studies do not overlap (repetition rate ≤ 50%), then we will retain both reviews [ 34 ].

We will present the findings as a narrative synthesis, and will take tabulated summaries and visualized evidenced map to display the data [ 35 ]. The presentation of results will follow a simple visual ’traffic light’ indicator, where green indicates that the intervention is beneficial, orange indicates that there is no difference in the comparison of the surveys, and red indicates that the results indicate that the intervention is harmful or less effective than the controls [ 36 ]. When results are not reported in the network meta-analysis, the indicator box is left blank. We will give recommendations for clinical use of agents based on evidence-based medical evidence. We will consider evidence to be sufficient if a systematic review is of high quality. On the contrary, we will not compute an overview meta-estimate due to the likelihood of considerable heterogeneity in study populations and outcomes between studies, the absence of essential meta-data and the lack of well-established quantification methods. Results of this overview will be reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [ 37 ]. The reasons for any amendments of protocol will be documented in the full review.

3. Discussion

This study will be the first overview of systematic reviews based on network meta-analysis. We will use rigorous methodology to seriously and systematically appraise and synthesis published systematic reviews with network meta-analysis evidence. The results of the many network meta-analysis overwhelm readers, and we hope to be able to summarise and sort them out further for users of the evidence. It is a great ambition to perform a secondary combined analysis of the data from the numerous network meta-analyses, and our team did not consider a combined analysis of the data in this work. Based on the published network meta-analysis, the efficacy and safety of various anti-hyperglycemic agents will be systematically reviewed and validated, and used GRADE to validate the quality of evidence from different studies to identify the most suitable treatment options for T2DM patients in different risk strata. We will provide new commentary and higher levels of evidence for the harm and benefits associated with diabetes medications [ 38 ]. The overview of reviews will provide a more comprehensive and integrated evidence-based opinion for guideline development, and make the rational use of drugs for T2DM patients more transparent and reliable. We expect the results of this comprehensive synthesis overview base-on network meta-analysis will benefit physicians, policy makers and developers of clinical guidelines for the management of T2DM patients with different risk stratifications. Furthermore, we also expect this overview of systematic review will improve the quality of secondary research in this field in the future and encourage more original research for those agents for which evidence is controversial or lacking in the current systematic reviews.

Supporting information

S1 checklist. prisma-p (preferred reporting items for systematic review and meta-analysis protocols) 2015 checklist: recommended items to address in a systematic review protocol*..


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Systematic reviews. Some examples.

Reviewing the literature is a scientific inquiry that needs a clear design to preclude bias. It is a real enterprise if one aims at completeness of the literature on a certain subject. Going through refereed English language journals is not enough. On line databases are helpful, but mainly as a starting point. This article gives examples of systematic reviews on vitamin C and the common cold, pyridoxine against the premenstrual syndrome, homeopathy, and physiotherapy.

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (916K), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References .

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Selected References

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