Preferred Reporting Items for Systematic Reviews and Meta-analyses the Prisma Statement

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Research Methods & Reporting

Preferred reporting items for systematic reviews and meta-analyses: the PRISMA argument

BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b2535 (Published 21 July 2009) Cite this equally: BMJ 2009;339:b2535

1. David Moher12,
2. Alessandro Liberati34,
3. Jennifer Tetzlaff1,
4. Douglas G Altmanfive
5. for the PRISMA Group

1. ¹Ottawa Methods Centre, Ottawa Hospital Research Establish, Ottawa, Ontario, Canada
2. ²Department of Epidemiology and Community Medicine, Faculty of Medicine, Academy of Ottawa, Ottawa, Ontario, Canada
3. ³Università di Modena e Reggio Emilia, Modena, Italy
4. ⁴Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri, Milan, Italy
5. ⁵Middle for Statistics in Medicine, Academy of Oxford, Oxford, United Kingdom

1. Correspondence to: dmoher{at}ohri.ca

• Accepted 5 June 2009

David Moher and colleagues innovate PRISMA, an update of the QUOROM guidelines for reporting systematic reviews and meta-analyses

Systematic reviews and meta-analyses have become increasingly important in wellness care. Clinicians read them to go on upwards to date with their specialty,1 ii and they are often used as a starting point for developing clinical practice guidelines. Granting agencies may require a systematic review to ensure there is justification for further research,3 and some medical journals are moving in this direction.four As with all enquiry, the value of a systematic review depends on what was done, what was constitute, and the clarity of reporting. As with other publications, the reporting quality of systematic reviews varies, limiting readers' power to assess the strengths and weaknesses of those reviews.

Several early studies evaluated the quality of review reports. In 1987 Mulrow examined 50 review manufactures published in iv leading medical journals in 1985 and 1986 and constitute that none met all 8 explicit scientific criteria, such as a quality assessment of included studies.5 In 1987 Sacks and colleagues evaluated the adequacy of reporting of 83 meta-analyses on 23 characteristics in six domains.6 Reporting was generally poor; between i and 14 characteristics were fairly reported (mean vii.7, standard deviation 2.7). A 1996 update of this report found picayune improvement.vii

In 1996, to address the suboptimal reporting of meta-analyses, an international group developed a guidance chosen the QUOROM argument (QUality Of Reporting Of Meta-analyses), which focused on the reporting of meta-analyses of randomised controlled trials.viii In this article, we summarise a revision of these guidelines, renamed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses), which take been updated to address several conceptual and applied advances in the science of systematic reviews (meet box).

Conceptual issues in the evolution from QUOROM to PRISMA

Completing a systematic review is an iterative process

The bear of a systematic review depends heavily on the telescopic and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Whatever systematic review reporting guideline should recommend that such changes tin exist reported and explained without suggesting that they are inappropriate. The PRISMA statement (items v, 11, sixteen, and 23) acknowledges this iterative procedure. Bated from Cochrane reviews, all of which should take a protocol, only about x% of systematic reviewers written report working from a protocol.nine Without a protocol that is publicly accessible, it is hard to judge between appropriate and inappropriate modifications.

Conduct and reporting of enquiry are singled-out concepts

This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and acquit of systematic reviews are, past nature, closely intertwined. For example, the failure of a systematic review to study the assessment of the take chances of bias in included studies may exist seen as a mark of poor conduct, given the importance of this activity in the systematic review process.ten

Report-level versus outcome-level assessment of risk of bias

For studies included in a systematic review, a thorough assessment of the risk of bias requires both a study-level cess (such as adequacy of allocation concealment) and, for some features, a newer approach called consequence-level assessment. An outcome-level assessment involves evaluating the reliability and validity of the data for each important outcome by determining the methods used to assess them in each individual study.11 The quality of bear witness may differ beyond outcomes, even within a study, such as between a primary efficacy outcome, which is likely to exist carefully and systematically measured, and the assessment of serious harms,12 which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit cess of the extent to which an estimate of result is right.11

Importance of reporting biases

Different types of reporting biases may hamper the behave and estimation of systematic reviews. Selective reporting of complete studies (such equally publication bias),thirteen equally well every bit the more recently empirically demonstrated "outcome reporting bias" within individual studies,fourteen 15 should exist considered by authors when conducting a systematic review and reporting its results. Although the implications of these biases on the conduct and reporting of systematic reviews themselves are unclear, some research has identified that selective issue reporting may occur also in the context of systematic reviews.xvi

Terminology

The terminology used to describe a systematic review and meta-assay has evolved over fourth dimension. One reason for changing the name from QUOROM to PRISMA was the desire to encompass both systematic reviews and meta-analyses. Nosotros have adopted the definitions used past the Cochrane Collaboration.17 A systematic review is a review of a clearly formulated question that uses systematic and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyse data from the studies that are included in the review. Statistical methods (meta-assay) may or may not exist used to analyse and summarise the results of the included studies. Meta-analysis refers to the use of statistical techniques in a systematic review to integrate the results of included studies.

Developing the PRISMA statement

A 3-day meeting was held in Ottawa, Canada, in June 2005 with 29 participants, including review authors, methodologists, clinicians, medical editors, and a consumer. The objective of the Ottawa meeting was to revise and expand the QUOROM checklist and menstruum diagram equally needed.

The executive committee completed the following tasks before the meeting: a systematic review of studies examining the quality of reporting of systematic reviews; a comprehensive literature search to identify methodological and other manufactures that might inform the meeting, especially in relation to modifying checklist items; and an international survey of review authors, consumers, and groups commissioning or using systematic reviews and meta-analyses (including the International Network of Agencies for Health Applied science Assessment and the Guidelines International Network) to ascertain views of QUOROM, including the merits of the existing checklist items. The results of these activities were presented during the meeting and are summarised on the PRISMA website, www.prisma-statement.org/.

Just items accounted essential were retained or added to the checklist. Some additional items are all the same desirable, and review authors should include these, if relevant.eighteen For case, it is useful to indicate whether the systematic review is an update of a previous review19 and to describe any changes in procedures from those described in the original protocol.

Shortly afterward the coming together, a typhoon of the PRISMA checklist was circulated to the group, including those invited to the meeting but unable to attend. A disposition file was created containing comments and revisions from each respondent, and the checklist was later on revised eleven times. The grouping canonical the checklist, flow diagram, and this summary newspaper.

Although no direct prove was institute to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, item v asks authors to provide registration data about the systematic review, including a registration number if available. Although systematic review registration is non still widely available,20 21 the participating journals of the International Commission of Medical Periodical Editors22 now require all clinical trials to exist registered in an effort to increment transparency and accountability.23 Those aspects are as well likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question24 25 and providing greater transparency when updating systematic reviews.

The PRISMA statement

The PRISMA statement consists of a 27 detail checklist (table 1⇓) and a four phase catamenia diagram (figure⇓) (also bachelor as extra items on bmj.com for researchers to download and re-apply). The aim of the PRISMA argument is to assistance authors better the reporting of systematic reviews and meta-analyses. We take focused on randomised trials, but PRISMA can too be used equally a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may likewise be useful for critical appraisement of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review.

Table 1

 Checklist of items to include when reporting a systematic review or meta-assay

From QUOROM to PRISMA

The new PRISMA checklist differs in several respects from the QUOROM checklist, and table 2⇓ lists the substantive specific changes. Generally, the PRISMA checklist "decouples" several items present in the QUOROM checklist and, where applicable, several checklist items are linked to improve consistency across the systematic review report.

Tabular array 2

 Noun specific changes betwixt the QUOROM checklist and the PRISMA checklist (a tick indicates the presence of the topic in QUOROM or PRISMA)

The flow diagram has also been modified. Before including studies and providing reasons for excluding others, the review team must first search the literature. This search results in records. Once these records have been screened and eligibility criteria applied, a smaller number of manufactures will remain. The number of included articles might be smaller (or larger) than the number of studies, because articles may report on multiple studies and results from a particular study may be published in several articles. To capture this information, the PRISMA menstruation diagram now requests information on these phases of the review process.

Endorsement

The PRISMA argument should replace the QUOROM statement for those journals that take endorsed QUOROM. Nosotros hope that other journals will support PRISMA; they tin can practise so by registering on the PRISMA website. To emphasise to authors and others the importance of transparent reporting of systematic reviews, we encourage supporting journals to reference the PRISMA argument and include the PRISMA web address in their instructions to authors. We too invite editorial organisations to consider endorsing PRISMA and encourage authors to adhere to its principles.

The PRISMA explanation and elaboration paper

In addition to the PRISMA statement, a supporting explanation and elaboration document has been produced26 following the fashion used for other reporting guidelines.27 28 29 The procedure of completing this document included developing a large database of exemplars to highlight how all-time to study each checklist item, and identifying a comprehensive evidence base to support the inclusion of each checklist item. The explanation and elaboration document was completed after several confront to face up meetings and numerous iterations among several coming together participants, after which information technology was shared with the whole group for boosted revisions and final approval. Finally, the group formed a broadcasting subcommittee to help disseminate and implement PRISMA.

Word

The quality of reporting of systematic reviews is still not optimal.9 30 31 32 33 34 In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias,9 even though in that location is overwhelming evidence for its existence13 and its impact on the results of systematic reviews.35 Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately.36 Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an cess of possible publication bias is probable to be a marking of the thoroughness of the bear of the systematic review.

Several approaches have been adult to conduct systematic reviews on a broader array of questions. For example, systematic reviews are now conducted to investigate toll effectiveness,37 diagnostic38 or prognostic questions,39 genetic associations,40 and policy making.41 The general concepts and topics covered by PRISMA are relevant to any systematic review, not simply those summarising the benefits and harms of a healthcare intervention. Withal, some modifications of the checklist items or flow diagram will be necessary in particular circumstances. For case, assessing the chance of bias is a key concept, merely the items used to assess this in a diagnostic review are likely to focus on issues such every bit the spectrum of patients and the verification of disease status, which differ from reviews of interventions. The catamenia diagram will besides demand adjustments when reporting meta-analysis of individual patient data.42

We have developed an explanatory certificate to increment the usefulness of PRISMA.26 For each checklist item, this document contains an example of good reporting, a rationale for its inclusion, and supporting evidence, including references, whenever possible. We believe this document will likewise serve as a useful resources for those educational activity systematic review methodology. Nosotros encourage journals to include reference to the explanatory document in their instructions to authors.

Like whatsoever evidence based effort, PRISMA is a living certificate. To this stop we invite readers to annotate on the revised version, peculiarly the new checklist and flow diagram, through the PRISMA website. We will use such data to inform PRISMA'due south continued development.

Notes

Cite this as: BMJ 2009;338:b2535

Footnotes

• The following people contributed to the PRISMA argument: Doug Altman, Centre for Statistics in Medicine (Oxford); Gerd Antes, University Hospital Freiburg (Freiburg, Frg); David Atkins, Health Services Inquiry and Development Service, Veterans Wellness Assistants (Washington DC, United states of america); Virginia Barbour, PLoS Medicine (Cambridge, United kingdom of great britain and northern ireland); Nick Barrowman, Children's Infirmary of Eastern Ontario (Ottawa, Canada); Jesse A. Berlin, Johnson & Johnson Pharmaceutical Research and Development (Titusville NJ, U.s.); Jocalyn Clark, PLoS Medicine (at the time of writing, BMJ, London); Mike Clarke, UK Cochrane Middle (Oxford) and Schoolhouse of Nursing and Midwifery, Trinity College (Dublin, Republic of ireland); Deborah Cook, Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University (Hamilton, Canada); Roberto D'Amico, Università di Modena e Reggio Emilia (Modena, Italy) and Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri (Milan, Italy); Jonathan J Deeks, University of Birmingham (Birmingham); P J Devereaux, Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University; Kay Dickersin, Johns Hopkins Bloomberg Schoolhouse of Public Health (Baltimore Doc, USA); Matthias Egger, Department of Social and Preventive Medicine, University of Bern (Bern, Switzerland); Edzard Ernst, Peninsula Medical School (Exeter, UK); Peter C Gøtzsche, Nordic Cochrane Center (Copenhagen, Kingdom of denmark); Jeremy Grimshaw, Ottawa Hospital Research Establish (Ottawa, Canada); Gordon Guyatt, Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University; Julian Higgins, MRC Biostatistics Unit of measurement (Cambridge, UK); John P A Ioannidis, Academy of Ioannina Campus (Ioannina, Hellenic republic); Jos Kleijnen, Kleijnen Systematic Reviews (York, UK) and School for Public Health and Primary Care (CAPHRI), University of Maastricht (Maastricht, Netherlands); Tom Lang, Tom Lang Communications and Training (Davis CA, The states); Alessandro Liberati, Università di Modena east Reggio Emilia, and Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri; Nicola Magrini, NHS Center for the Evaluation of the Effectiveness of Wellness Care—CeVEAS (Modena, Italy); David McNamee, Lancet (London, Uk); Lorenzo Moja, Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri; David Moher, Ottawa Methods Centre, Ottawa Hospital Research Institute (Ottawa, Canada); Cynthia Mulrow, Annals of Internal Medicine (Philadelphia PA, Usa); Maryann Napoli, Middle for Medical Consumers (New York, United states); Andy Oxman, Norwegian Health Services Research Centre (Oslo, Norway); Ba' Pham, Toronto Health Economics and Technology Assessment Collaborative (Toronto, Canada) (at the time of outset meeting of the group, GlaxoSmithKline Canada, Mississauga, Ontario); Drummond Rennie, Academy of California San Francisco (San Francisco CA, Us); Margaret Sampson, Children'due south Hospital of Eastern Ontario (Ottawa, Canada); Kenneth F Schulz, Family unit Health International (Durham NC, USA); Paul K Shekelle, Southern California Testify Based Practice Center (Santa Monica CA, Usa); Jennifer Tetzlaff, Ottawa Methods Centre, Ottawa Infirmary Research Institute; David Tovey, Cochrane Library, Cochrane Collaboration (Oxford, UK) (at the time of first meeting of the grouping, BMJ, London); Peter Tugwell, Institute of Population Health, University of Ottawa (Ottawa, Canada).

• Author contributions: ICMJE criteria for authorship read and met—DM. Concord with the recommendations—DM, AL, JT, DGA. Wrote the beginning typhoon of the paper—DM, AL, DGA. Contributed to the writing of the paper—DM, AL, JT, DGA. Participated in regular conference calls, identified the participants, secured funds, planned the meeting, participated in the meeting, and drafted the manuscript—DM, AL, DGA. Participated in identifying the evidence base of operations for PRISMA, refining the checklist, and drafting the manuscript—JT.

• Funding: PRISMA was funded by the Canadian Institutes of Health Research; Università di Modena east Reggio Emilia, Italy; Cancer Research UK; Clinical Show BMJ Knowledge; the Cochrane Collaboration; and GlaxoSmithKline, Canada. AL is funded, in part, through grants of the Italian Ministry building of University (COFIN-PRIN 2002 prot 2002061749 and COFIN-PRIN 2006 prot 2006062298). DGA is funded by Cancer Research U.k.. DM is funded by a Academy of Ottawa Research Chair. None of the sponsors had any involvement in the planning, execution, or writing of the PRISMA documents. No funder played a role in drafting this manuscript.

• Competing interests: None alleged.

• Provenance and peer review: Not commissioned; externally peer reviewed.

• In club to encourage dissemination of the PRISMA statement, this article is freely attainable on bmj.com and will also be published in PLoS Medicine, Annals of Internal Medicine, Periodical of Clinical Epidemiology, and Open Medicine. The authors jointly concur the copyright of this article. For details on further employ, run across the PRISMA website (world wide web.prisma-statement.org/).

This is an open-access article distributed under the terms of the Artistic Commons Attribution Not-commercial License, which permits unrestricted utilise, distribution, and reproduction in any medium, provided the original work is properly cited.

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