David MoherpersName, Alessandro LiberatipersName, Jennifer TetzlaffpersName, Douglas G. AltmanpersName (2009date). “Preferred Reporting Items for Systematic Reviews and Meta-Analyses: The PRISMA Statement.” PLOS Medicinetitle·j, OttawaplaceName.
Object of study — How systematic reviewsterm·mth and meta-analyses of medical evidenceterm·key should be reported.
Research question — What minimum set of items must a systematic reviewterm·mth report so its methods and findings can be appraised and reproduced?
Contribution — Establishes the PRISMAterm·mth reporting standardterm·dom - a checklistterm·mth and flow diagramterm·mth for systematic reviewsterm·mth - underpinning evidence-based medicine and transparentterm·key synthesis.
phenomenon · claim-type · cross-domain-transfer · mechanism · claim-relation · replication-status · limitation — grounded in the full text| phenomenon | reporting quality of systematic reviews and meta-analyses — “As with other publications, the reporting quality of systematic reviews varies, limiting readers' ability to assess the strengths and weaknesses of those reviews.” | |
| claim-type | method — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use).” | |
| method — evidence | — “A three-day meeting was held in Ottawa, Canada, in June 2005 with 29 participants, including review authors, methodologists, clinicians, medical editors, and a consumer.” | |
| object of study — evidence | — “As with other publications, the reporting quality of systematic reviews varies, limiting readers' ability to assess the strengths and weaknesses of those reviews.” | |
| research question — evidence | — “The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses.” | |
| transfer | from statistics (meta-analysis): statistical meta-analysis methodology for pooling and summarizing results across studies, standardized as a transparent reporting standard for medical evidence synthesis — “Statistical methods (meta-analysis) may or may not be used to analyze and summarize the results of the included studies” | transfers[0] |
| mechanism | A checklist works by making omissions visible: an item not reported becomes conspicuous rather than merely absent — “Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review.” | mechanisms[0] |
| mechanism | Items were admitted only if essential, so the checklist's authority rests on being a floor rather than a wish list — “Only items deemed essential were retained or added to the checklist.” | mechanisms[1] |
| mechanism | Where direct evidence for an item was absent, evidence from adjacent domains was accepted instead - registration is justified by the trial-registration precedent, not by studies of review registration — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant.” | mechanisms[2] |
| mechanism | The checklist decouples items that QUOROM had bundled, and links others, so that consistency across a report can be checked item by item — “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.” | mechanisms[3] |
| mechanism | A separate Explanation and Elaboration document carries the exemplars and the evidence for each item, keeping the statement itself short enough to use — “For each checklist item, this document contains an example of good reporting, a rationale for its inclusion, and supporting evidence, including references, whenever possible.” | mechanisms[4] |
| extends | the QUOROM reporting checklist — “revise and expand the QUOROM checklist and flow diagram” | claim_relations[0] |
| extends | the QUOROM Statement (Quality Of Reporting Of Meta-analyses) — “In this article, we summarize a revision of these guidelines, renamed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses), which have been updated to address several conceptual and practical advances in the science of systematic reviews ( Box 1 ).” | claim_relations[1] |
| builds-on | the Cochrane Collaboration definitions of systematic review and meta-analysis — “We have adopted the definitions used by the Cochrane Collaboration [9] .” | claim_relations[2] |
| extends | the QUOROM Statement, which PRISMA revises, renames and is intended to replace — “In this article, we summarize a revision of these guidelines, renamed PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses), which have been updated to address several conceptual and practical advances in the science of systematic reviews ( Box 1 ).” | claim_relations[3] |
| supports | Mulrow 1987 and Sacks et al. 1987 on the poor reporting quality of reviews — “In 1987, Mulrow examined 50 review articles published in four leading medical journals in 1985 and 1986 and found that none met all eight explicit scientific criteria, such as a quality assessment of included studies [5] .” | claim_relations[4] |
| extends | the ICMJE trial-registration requirement, used as the precedent for review registration — “the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15]” | claim_relations[5] |
| extends | the Cochrane Collaboration's definitions of systematic review and meta-analysis — “We have adopted the definitions used by the Cochrane Collaboration [9] .” | claim_relations[6] |
| sense | risk of bias - study-level: a property of how the whole study was designed and run, e.g. adequacy of allocation concealment — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-level” assessment.” | senses[0] |
| sense | risk of bias - outcome-level: assessed separately per outcome, because quality can differ within one study between a primary efficacy measure and the recording of harms — “The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators.” | senses[1] |
| sense | reporting bias - publication bias: whole studies going unreported — “Selective reporting of complete studies (e.g., publication bias) [28] as well as the more recently empirically demonstrated “outcome reporting bias” within individual studies [40] , [41] should be considered by authors when conducting a systematic review and reporting its results.” | senses[2] |
| sense | reporting bias - outcome reporting bias: outcomes going unreported within a study that was itself published — “as well as the more recently empirically demonstrated “outcome reporting bias” within individual studies” | senses[3] |
| sense | the unit of counting - record: what the search returns, before anything is screened — “Before including studies and providing reasons for excluding others, the review team must first search the literature. This search results in records.” | senses[4] |
| sense | the unit of counting - article versus study: not interchangeable, because one article can report several studies and one study can appear in several articles — “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.” | senses[5] |
| sense | conduct versus reporting: nominally distinct, but for systematic reviews a failure to report can itself be read as a marker of poor conduct — “For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process [37] .” | senses[6] |
| sense | Systematic review - explicit question, systematic identification and appraisal, and collection and analysis of included-study data — “The terminology used to describe a systematic review and meta-analysis has evolved over time. One reason for changing the name from QUOROM to PRISMA was the desire to encompass both systematic reviews and meta-analyses. We have adopted the definitions used by the Cochrane Collaboration [9] . 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 analyze data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyze and summarize 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” | senses[7] |
| sense | Meta-analysis - statistical integration used within a systematic review, but not required for every systematic review — “The terminology used to describe a systematic review and meta-analysis has evolved over time. One reason for changing the name from QUOROM to PRISMA was the desire to encompass both systematic reviews and meta-analyses. We have adopted the definitions used by the Cochrane Collaboration [9] . 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 analyze data from the studies that are included in the review. Statistical methods (meta-analysis) may or may not be used to analyze and summarize 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” | senses[8] |
| sense | Iterative systematic review - protocol changes may be appropriate when included-study scope or quality changes — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | senses[9] |
| sense | Conduct / reporting distinction - nominally separate but closely intertwined for systematic reviews — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | senses[10] |
| sense | Study-level / outcome-level risk of bias - whole-study design assessment plus outcome-specific reliability and validity — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | senses[11] |
| sense | Essential checklist item - retained or added only when the consensus group judged it essential — “Only items deemed essential were retained or added to the checklist. Some additional items are nevertheless desirable, and review authors should include these, if relevant [10] . For example, it is useful to indicate whether the systematic review is an update [11] of a previous review, and to describe any changes in procedures from those described in the original protocol” | senses[12] |
| sense | Review registration - transparency precedent with a possible role in reducing duplicate reviews — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, Item 5 asks authors to provide registration information about the systematic review, including a registration number, if available. Although systematic review registration is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15] . Those aspects are also likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question [16] , [17] and providing greater transparency when updating systematic reviews” | senses[13] |
| sense | PRISMA instrument - 27-item checklist and four-phase flow diagram for reporting improvement — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | senses[14] |
| sense | PRISMA scope - randomized-trial focus, extensible to other research and critical appraisal, but not a review-quality scale — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | senses[15] |
| sense | PRISMA flow units - records become articles after screening and eligibility, while article and study counts can diverge — “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 articles 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 flow diagram now requests information on these phases of the review process” | senses[16] |
| sense | Explanation and Elaboration - companion exemplars, rationales, and evidence bases for checklist items — “In addition to the PRISMA Statement, a supporting Explanation and Elaboration document has been produced [18] following the style used for other reporting guidelines [19] – [21] . The process of completing this document included developing a large database of exemplars to highlight how best to report 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 face to face meetings and numerous iterations among several meeting participants, after which it was shared with the whole group for additional revisions and final approval. Finally, the group formed a dissemination subcommittee to help disseminate and implement PRISMA” | senses[17] |
| sense | Bias-assessment reporting - imperfect evidence that nevertheless marks thorough review conduct — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | senses[18] |
| sense | Cross-domain PRISMA - general concepts persist across review questions while concrete bias items and flow diagrams require adaptation — “Several approaches have been developed to conduct systematic reviews on a broader array of questions. For example, systematic reviews are now conducted to investigate cost-effectiveness [31] , diagnostic [32] or prognostic questions [33] , genetic associations [34] , and policy making [35] . The general concepts and topics covered by PRISMA are all relevant to any systematic review, not just those whose objective is to summarize the benefits and harms of a health care intervention. However, some modifications of the checklist items or flow diagram will be necessary in particular circumstances. For example, assessing the risk of bias is a key concept, but the items used to assess this in a diagnostic review are likely to focus on issues such as the spectrum of patients and the verification of disease status, which differ from reviews of interventions. The flow diagram will also need adjustments when reporting individual patient data meta-analysis” | senses[19] |
| sense | Living PRISMA - reader feedback is intended to inform continued guideline development — “Like any evidence-based endeavor, PRISMA is a living document. To this end we invite readers to comment on the revised version, particularly the new checklist and flow diagram, through the PRISMA Web site. We will use such information to inform PRISMA's continued development” | senses[20] |
| audit | PRISMA —renamed-across-fields→ QUOROM — Audit 2026-09-28: DOUBTFUL - read against its span and kept, but the span records a name change within one field; renamed-across-fields overstates it. — “One reason for changing the name from QUOROM to PRISMA was the desire to encompass both systematic reviews and meta-analyses.” | concept_edges[0] |
| audit | PRISMA —distinct-from→ QUOROM — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span says PRISMA should REPLACE QUOROM; distinct-from is loose. — “The PRISMA Statement should replace the QUOROM Statement for those journals that have endorsed QUOROM.” | concept_edges[1] |
| edge | meta-analysis —part-of→ systematic review — “Meta-analysis refers to the use of statistical techniques in a systematic review to integrate the results of included studies.” | concept_edges[2] |
| audit | outcome reporting bias —is-a→ reporting biases — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but endpoint by anaphora: the span enumerates the 'different types of reporting biases' named in the previous sentence. — “Selective reporting of complete studies (e.g., publication bias) [28] as well as the more recently empirically demonstrated “outcome reporting bias” within individual studies [40] , [41] should be considered by authors when conducting a systematic review and reporting its results.” | concept_edges[4] |
| edge | articles —distinct-from→ studies — “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.” | concept_edges[5] |
| audit | records —distinct-from→ articles — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span says fewer articles remain after records are screened; distinct-from is loose. — “Once these records have been screened and eligibility criteria applied, a smaller number of articles will remain.” | concept_edges[6] |
| audit | PRISMA —operationalised-as→ checklist — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span says PRISMA CONSISTS OF a checklist and a flow diagram; operationalised-as is loose. — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use).” | concept_edges[7] |
| audit | Explanation and Elaboration —part-of→ PRISMA — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span calls Explanation and Elaboration a SUPPORTING document in addition to the Statement; part-of is loose. — “In addition to the PRISMA Statement, a supporting Explanation and Elaboration document has been produced [18] following the style used for other reporting guidelines [19] – [21] .” | concept_edges[12] |
| edge | flow diagram —part-of→ PRISMA — “To capture this information, the PRISMA flow diagram now requests information on these phases of the review process.” | concept_edges[14] |
| note | study-level —contrasted-with→ outcome-level — The section explicitly sets study-level versus outcome-level assessment, then requires both. — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | concept_edges[16] |
| relation | study-level —contrasted-with→ outcome-level — Study-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” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | concept_edges[16] |
| audit | Conduct —distinct-from→ Reporting — Audit 2026-09-28: DOUBTFUL - read against its full span and kept, but the span says the distinction is LESS STRAIGHTFORWARD for systematic reviews because conduct and reporting are intertwined; hedged. — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | concept_edges[17] |
| note | Conduct —distinct-from→ Reporting — Weight reflects the paper's qualification that the nominal distinction is less straightforward for reviews. — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | concept_edges[17] |
| relation | Conduct —distinct-from→ Reporting — Conduct and Reporting Research Are Distinct Concepts This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | concept_edges[17] |
| weight | Conduct —distinct-from→ Reporting — 0.8 — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | concept_edges[17] |
| note | 27-item checklist —part-of→ PRISMA — PRISMA is explicitly stated to consist of the checklist and flow diagram. — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | concept_edges[18] |
| note | four-phase flow diagram —part-of→ PRISMA — PRISMA is explicitly stated to consist of the checklist and flow diagram. — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | concept_edges[19] |
| audit | several checklist items —causes→ consistency across the systematic review report — Audit 2026-09-28: DOUBTFUL - read against its span and kept, but checklist items are linked 'to improve consistency'; causes states the aim as an effect. — “The new PRISMA checklist differs in several respects from the QUOROM checklist, and the substantive specific changes are highlighted in Table 2 . 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” | concept_edges[20] |
| note | several checklist items —causes→ consistency across the systematic review report — The paper states the intended effect ('linked to improve'); weight is below one because this is a design aim, not an outcome test. — “The new PRISMA checklist differs in several respects from the QUOROM checklist, and the substantive specific changes are highlighted in Table 2 . 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” | concept_edges[20] |
| weight | several checklist items —causes→ consistency across the systematic review report — 0.9 — “The new PRISMA checklist differs in several respects from the QUOROM checklist, and the substantive specific changes are highlighted in Table 2 . 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” | concept_edges[20] |
| note | publication bias —causes→ results of systematic reviews — The paper says overwhelming evidence exists for publication bias's impact on review results. — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | concept_edges[21] |
| for which use | limitation — any inference from a missing item to what the reviewers did: THE ABSENCE OF REPORTING SUCH AN ASSESSMENT DOES NOT NECESSARILY INDICATE THAT IT WAS NOT DONE — “the absence of reporting such an assessment does not necessarily indicate that it was not done” | limitations[0] |
| for which use | limitation — quality assessment, named as the use the instrument does not support: THE PRISMA CHECKLIST IS NOT A QUALITY ASSESSMENT INSTRUMENT TO GAUGE THE QUALITY OF A SYSTEMATIC REVIEW — “However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review.” | limitations[1] |
| for which use | limitation — the evidential standing of the checklist itself: ALTHOUGH NO DIRECT EVIDENCE WAS FOUND TO SUPPORT RETAINING OR ADDING SOME ITEMS, EVIDENCE FROM OTHER DOMAINS WAS BELIEVED TO BE RELEVANT — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant.” | limitations[2] |
| for which use | limitation — review types other than interventions: SOME MODIFICATIONS OF THE CHECKLIST ITEMS OR FLOW DIAGRAM WILL BE NECESSARY IN PARTICULAR CIRCUMSTANCES — “However, some modifications of the checklist items or flow diagram will be necessary in particular circumstances.” | limitations[3] |
| for which use | limitation — reviews of randomized trials, which is what it was built for: WE HAVE FOCUSED ON RANDOMIZED TRIALS, BUT PRISMA CAN ALSO BE USED AS A BASIS FOR REPORTING SYSTEMATIC REVIEWS OF OTHER TYPES OF RESEARCH, PARTICULARLY EVALUATIONS OF INTERVENTIONS — “We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions.” | limitations[4] |
| duplicate of | limitation — limitations[1] — “However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review.” | limitations[5] |
| for which use | limitation — the same scope as limitations[1] - reporting, not quality, said explicitly to head off misuse — “However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review.” | limitations[5] |
| duplicate of | limitation — limitations[3] — “However, some modifications of the checklist items or flow diagram will be necessary in particular circumstances.” | limitations[6] |
| for which use | limitation — the same scope as limitations[3] - the checklist was developed with randomized trials in view — “However, some modifications of the checklist items or flow diagram will be necessary in particular circumstances.” | limitations[6] |
| for which use | limitation — the conduct-versus-reporting distinction the whole instrument rests on: THIS DISTINCTION IS, HOWEVER, LESS STRAIGHTFORWARD FOR SYSTEMATIC REVIEWS THAN FOR ASSESSMENTS OF THE REPORTING OF AN INDIVIDUAL STUDY, BECAUSE THE REPORTING AND CONDUCT OF SYSTEMATIC REVIEWS ARE, BY NATURE, CLOSELY INTERTWINED — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined.” | limitations[7] |
| for which use | limitation — the protocol-comparison item, which most reviews cannot answer: ASIDE FROM COCHRANE REVIEWS, ALL OF WHICH SHOULD HAVE A PROTOCOL, ONLY ABOUT 10% OF SYSTEMATIC REVIEWERS REPORT WORKING FROM A PROTOCOL — “Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] .” | limitations[8] |
| for which use | limitation — whether reporting biases bite on systematic reviews themselves: THE IMPLICATIONS OF THESE BIASES ON THE CONDUCT AND REPORTING OF SYSTEMATIC REVIEWS THEMSELVES ARE UNCLEAR — “Though the implications of these biases on the conduct and reporting of systematic reviews themselves are unclear, some previous research has identified that selective outcome reporting may occur also in the context of systematic reviews [42] .” | limitations[9] |
| for which use | limitation — any treatment of the document as fixed: LIKE ANY EVIDENCE-BASED ENDEAVOR, PRISMA IS A LIVING DOCUMENT — “Like any evidence-based endeavor, PRISMA is a living document.” | limitations[10] |
| relation | conduct of a systematic review → scope and quality of included studies — Completing a Systematic Review Is an Iterative Process The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | unhoused_relations[0] |
| relation | quality of evidence → outcomes — Study-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” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | unhoused_relations[1] |
| weight | quality of evidence → outcomes — 0.8 — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | unhoused_relations[1] |
| weight | systematic review registration → risk of an excessive number of reviews addressing the same question — 0.5 — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, Item 5 asks authors to provide registration information about the systematic review, including a registration number, if available. Although systematic review registration is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15] . Those aspects are also likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question [16] , [17] and providing greater transparency when updating systematic reviews” | unhoused_relations[2] |
| weight | reporting an assessment of possible publication bias → thoroughness of the conduct of the systematic review — 0.8 — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | unhoused_relations[3] |
| replication | untested | |
| no type for this | conduct of a systematic review → scope and quality of included studies — The conduct of a review depends on included-study scope and quality; depends-on is absent, while none of the eight types expresses dependency. — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | unhoused_relations[0] |
| no type for this | quality of evidence → outcomes — Evidence quality may vary across outcomes within one study; varies-across is absent, and this is neither contrast nor containment between the endpoints. — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | unhoused_relations[1] |
| no type for this | systematic review registration → risk of an excessive number of reviews addressing the same question — Review registration may reduce duplicate reviews; may-reduce is absent, and forcing causes would erase the paper's 'possibly' hedge. — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, Item 5 asks authors to provide registration information about the systematic review, including a registration number, if available. Although systematic review registration is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15] . Those aspects are also likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question [16] , [17] and providing greater transparency when updating systematic reviews” | unhoused_relations[2] |
| no type for this | reporting an assessment of possible publication bias → thoroughness of the conduct of the systematic review — Reporting a publication-bias assessment is treated as a marker of conduct thoroughness; indicates is absent from the eight relation types. — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | unhoused_relations[3] |
| no type for this | example of good reporting → Explanation and Elaboration — The companion document contains an example for every checklist item; contains is absent and reversing it into part-of would make the document an endpoint not stated as a whole in the clause. — “In addition to the PRISMA Statement, a supporting Explanation and Elaboration document has been produced [18] following the style used for other reporting guidelines [19] – [21] . The process of completing this document included developing a large database of exemplars to highlight how best to report 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 face to face meetings and numerous iterations among several meeting participants, after which it was shared with the whole group for additional revisions and final approval. Finally, the group formed a dissemination subcommittee to help disseminate and implement PRISMA” | unhoused_relations[4] |
| limitation | absence of a reported bias-assessment does not necessarily mean it was not performed — “the absence of reporting such an assessment does not necessarily indicate that it was not done” | limitations[0] |
| limitation | The checklist reports on reporting only; it does not measure the quality of a review. — “However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review.” | limitations[1] |
| limitation | Some items were retained or added without direct supporting evidence. — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant.” | limitations[2] |
| limitation | The checklist and flow diagram will need modification for review types other than interventions. — “However, some modifications of the checklist items or flow diagram will be necessary in particular circumstances.” | limitations[3] |
| limitation | The statement was developed with randomized trials in mind. — “We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions.” | limitations[4] |
| limitation | The checklist governs reporting, not quality, and the authors say so explicitly to head off misuse — “However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review.” | limitations[5] |
| limitation | Developed with randomized trials in view, so other review types need modified items — “However, some modifications of the checklist items or flow diagram will be necessary in particular circumstances.” | limitations[6] |
| limitation | For systematic reviews the conduct/reporting distinction that the guideline depends on is itself blurred — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined.” | limitations[7] |
| limitation | Judging whether a mid-review change was appropriate requires a public protocol, and only about a tenth of reviewers report having one — “Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] .” | limitations[8] |
| limitation | Whether reporting biases affect systematic reviews themselves is acknowledged as unclear — “Though the implications of these biases on the conduct and reporting of systematic reviews themselves are unclear, some previous research has identified that selective outcome reporting may occur also in the context of systematic reviews [42] .” | limitations[9] |
| limitation | The document is explicitly provisional and expected to change — “Like any evidence-based endeavor, PRISMA is a living document.” | limitations[10] |
finding · quantity · variable · definition · key-term — grounded in the full text| finding | PRISMA consists of a 27-item checklist and a four-phase flow diagram, revising and expanding the QUOROM checklist and flow diagram. — “The PRISMA Statement consists of a 27-item checklist (Table 1...) and a four-phase flow diagram... to revise and expand the QUOROM checklist and flow diagram, as needed.” [checked against the archived source, not this rendering] | content_tags.findings[0] |
| not machine-vouched | finding — declared-ellipsis - An elided quote: its 3 pieces ('The PRISMA Statement consists of a 27-it' ... 'M checklist and flow diagram, as needed.') are each in our copy of the paper (with line-break hyphens, spacing and punctuation set aside), and the quote marks the cut with an ellipsis, so the joined string is in no copy. Located mechanically, piece by piece. | content_tags.findings[0] |
| finding | The value of a systematic review depends on what was done, what was found, and the clarity of reporting. — “the value of a systematic review depends on what was done, what was found, and the clarity of reporting” | content_tags.findings[1] |
| finding | the quality of reporting of systematic reviews is still not optimal — “The quality of reporting of systematic reviews is still not optimal [22] – [27] .” | content_tags.findings[2] |
| finding | few authors of systematic reviews report assessing publication bias, despite strong evidence it exists and affects results — “In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] .” | content_tags.findings[3] |
| finding | a 1996 update of this study found little improvement — “A 1996 update of this study found little improvement [7] .” | content_tags.findings[4] |
| finding | systematic review methodology has spread well beyond intervention questions, to cost-effectiveness, diagnosis, prognosis, genetics and policy — “For example, systematic reviews are now conducted to investigate cost-effectiveness [31] , diagnostic [32] or prognostic questions [33] , genetic associations [34] , and policy making [35] .” | content_tags.findings[5] |
| quantity | 27 items — number of items in the PRISMA checklist — “The PRISMA Statement consists of a 27-item checklist” | content_tags.quantities[0] |
| quantity | four-phase — phases in the PRISMA flow diagram — “and a four-phase flow diagram” | content_tags.quantities[1] |
| quantity | 27-item checklist — the size of the instrument itself — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use).” | content_tags.quantities[2] |
| quantity | 29 participants — the size of the consensus meeting that produced it — “A three-day meeting was held in Ottawa, Canada, in June 2005 with 29 participants, including review authors, methodologists, clinicians, medical editors, and a consumer.” | content_tags.quantities[3] |
| quantity | revised 11 times — how many iterations the checklist went through after the meeting — “A disposition file was created containing comments and revisions from each respondent, and the checklist was subsequently revised 11 times.” | content_tags.quantities[4] |
| quantity | about 10% — share of systematic reviewers reporting they worked from a protocol, outside Cochrane — “Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] .” | content_tags.quantities[5] |
| quantity | mean = 7.7; standard deviation = 2.7 — characteristics adequately reported out of 23, in Sacks et al.'s 1987 assessment of 83 meta-analyses — “Reporting was generally poor; between one and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7).” | content_tags.quantities[6] |
| quantity | none met all eight explicit scientific criteria — Mulrow's 1987 result across 50 review articles — “In 1987, Mulrow examined 50 review articles published in four leading medical journals in 1985 and 1986 and found that none met all eight explicit scientific criteria, such as a quality assessment of included studies [5] .” | content_tags.quantities[7] |
| definition | systematic review — “Systematic reviews and meta-analyses have become increasingly important in health care” | content_tags.definitions[0] |
| definition | meta-analysis — “Statistical methods (meta-analysis) may or may not be used to analyze and summarize the results of the included studies” | content_tags.definitions[1] |
| definition | PRISMA checklist — “The PRISMA Statement consists of a 27-item checklist” | content_tags.definitions[2] |
| definition | systematic review — “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 analyze data from the studies that are included in the review.” | content_tags.definitions[3] |
| definition | meta-analysis — “Meta-analysis refers to the use of statistical techniques in a systematic review to integrate the results of included studies.” | content_tags.definitions[4] |
| definition | outcome-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 [38] .” | content_tags.definitions[5] |
| definition | QUOROM — “an international group developed a guidance called the QUOROM Statement ( QU ality O f R eporting O f M eta-analyses), which focused on the reporting of meta-analyses of randomized controlled trials [8]” | content_tags.definitions[6] |
| definition | records — “Before including studies and providing reasons for excluding others, the review team must first search the literature. This search results in records.” | content_tags.definitions[7] |
| key-terms | PRISMA, systematic, review, meta-analysis, reporting, checklist, transparent, studies, evidence, systematic review, QUOROM, flow diagram, risk of bias, publication bias, outcome reporting bias, reporting biases, protocol, registration, eligibility criteria, Cochrane Collaboration |
| concept | PRISMA — not defined in this paper's own words; the 27-item checklist and four-phase flow diagram this paper introduces — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use).” | concepts[4] |
| concept | reporting quality — not defined in this paper's own words; clarity and completeness that determine whether readers can assess a review — “Systematic reviews and meta-analyses have become increasingly important in health care. Clinicians read them to keep up to date with their field [1] , [2] , 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 health care journals are moving in this direction [4] . As with all research, the value of a systematic review depends on what was done, what was found, and the clarity of reporting. As with other publications, the reporting quality of systematic reviews varies, limiting readers' ability to assess the strengths and weaknesses of those reviews” | concepts[20] |
| concept | iterative process — not defined in this paper's own words; protocol modification during a review in response to the included evidence — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | concepts[21] |
| concept | conduct of a systematic review — not defined in this paper's own words; review work whose course depends on the evidence included — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | concepts[22] |
| concept | scope and quality of included studies — not defined in this paper's own words; properties of included studies that can force protocol changes — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | concepts[23] |
| concept | appropriate and inappropriate modifications — not defined in this paper's own words; distinction made assessable by a public review protocol — “The conduct of a systematic review depends heavily on the scope and quality of included studies: thus systematic reviewers may need to modify their original review protocol during its conduct. Any systematic review reporting guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMA Statement (Items 5, 11, 16, and 23) acknowledges this iterative process. Aside from Cochrane reviews, all of which should have a protocol, only about 10% of systematic reviewers report working from a protocol [22] . Without a protocol that is publicly accessible, it is difficult to judge between appropriate and inappropriate modifications” | concepts[24] |
| concept | Conduct — not defined in this paper's own words; what reviewers do, nominally distinct from what they report — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | concepts[25] |
| concept | Reporting — not defined in this paper's own words; what reviewers disclose, closely intertwined with conduct for systematic reviews — “This distinction is, however, less straightforward for systematic reviews than for assessments of the reporting of an individual study, because the reporting and conduct of systematic reviews are, by nature, closely intertwined. For example, the failure of a systematic review to report the assessment of the risk of bias in included studies may be seen as a marker of poor conduct, given the importance of this activity in the systematic review process” | concepts[26] |
| concept | study-level — not defined in this paper's own words; whole-study risk-of-bias assessment such as allocation concealment — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | concepts[27] |
| concept | outcome-level — not defined in this paper's own words; risk-of-bias assessment performed separately for important outcomes — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | concepts[28] |
| concept | reliability and validity — not defined in this paper's own words; properties evaluated for each important outcome — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | concepts[29] |
| concept | quality of evidence — not defined in this paper's own words; evidential quality that can differ between outcomes within one study — “For studies included in a systematic review, a thorough assessment of the risk of bias requires both a “study-level” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-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 [38] . The quality of evidence may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct” | concepts[30] |
| concept | Selective reporting of complete studies — not defined in this paper's own words; whole-study selection mechanism exemplified by publication bias — “Different types of reporting biases may hamper the conduct and interpretation of systematic reviews. Selective reporting of complete studies (e.g., publication bias) [28] as well as the more recently empirically demonstrated “outcome reporting bias” within individual studies [40] , [41] should be considered by authors when conducting a systematic review and reporting its results. Though the implications of these biases on the conduct and reporting of systematic reviews themselves are unclear, some previous research has identified that selective outcome reporting may occur also in the context of systematic reviews” | concepts[31] |
| concept | selective outcome reporting — not defined in this paper's own words; selective reporting that can occur within studies and reviews — “Different types of reporting biases may hamper the conduct and interpretation of systematic reviews. Selective reporting of complete studies (e.g., publication bias) [28] as well as the more recently empirically demonstrated “outcome reporting bias” within individual studies [40] , [41] should be considered by authors when conducting a systematic review and reporting its results. Though the implications of these biases on the conduct and reporting of systematic reviews themselves are unclear, some previous research has identified that selective outcome reporting may occur also in the context of systematic reviews” | concepts[32] |
| concept | systematic review registration — not defined in this paper's own words; prospective registration proposed for transparency and duplicate-review control — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, Item 5 asks authors to provide registration information about the systematic review, including a registration number, if available. Although systematic review registration is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15] . Those aspects are also likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question [16] , [17] and providing greater transparency when updating systematic reviews” | concepts[33] |
| concept | transparency and accountability — not defined in this paper's own words; stated purpose of mandatory clinical-trial registration and expected review benefit — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, Item 5 asks authors to provide registration information about the systematic review, including a registration number, if available. Although systematic review registration is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15] . Those aspects are also likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question [16] , [17] and providing greater transparency when updating systematic reviews” | concepts[34] |
| concept | risk of an excessive number of reviews addressing the same question — not defined in this paper's own words; possible duplication cost that registration may reduce — “Although no direct evidence was found to support retaining or adding some items, evidence from other domains was believed to be relevant. For example, Item 5 asks authors to provide registration information about the systematic review, including a registration number, if available. Although systematic review registration is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountability [15] . Those aspects are also likely to benefit systematic reviewers, possibly reducing the risk of an excessive number of reviews addressing the same question [16] , [17] and providing greater transparency when updating systematic reviews” | concepts[35] |
| concept | 27-item checklist — not defined in this paper's own words; PRISMA reporting checklist with twenty-seven items — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | concepts[36] |
| concept | four-phase flow diagram — not defined in this paper's own words; PRISMA diagram tracking four phases of review information flow — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | concepts[37] |
| concept | critical appraisal — not defined in this paper's own words; secondary use of PRISMA for examining published reviews — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | concepts[38] |
| concept | quality assessment instrument — not defined in this paper's own words; instrument role explicitly denied to the PRISMA checklist — “The PRISMA Statement consists of a 27-item checklist ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagram ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. We have focused on randomized trials, but PRISMA can also be used as a basis for reporting systematic reviews of other types of research, particularly evaluations of interventions. PRISMA may also be useful for critical appraisal of published systematic reviews. However, the PRISMA checklist is not a quality assessment instrument to gauge the quality of a systematic review” | concepts[39] |
| concept | several checklist items — not defined in this paper's own words; cross-linked checklist entries intended to improve report consistency — “The new PRISMA checklist differs in several respects from the QUOROM checklist, and the substantive specific changes are highlighted in Table 2 . 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” | concepts[40] |
| concept | consistency across the systematic review report — not defined in this paper's own words; cross-report coherence targeted by linking PRISMA items — “The new PRISMA checklist differs in several respects from the QUOROM checklist, and the substantive specific changes are highlighted in Table 2 . 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” | concepts[41] |
| concept | example of good reporting — not defined in this paper's own words; exemplar supplied for each checklist item in the companion document — “For each checklist item, this document contains an example of good reporting, a rationale for its inclusion, and supporting evidence, including references, whenever possible.” | concepts[42] |
| concept | rationale for its inclusion — not defined in this paper's own words; reason supplied for each checklist item's presence — “For each checklist item, this document contains an example of good reporting, a rationale for its inclusion, and supporting evidence, including references, whenever possible.” | concepts[43] |
| concept | supporting evidence — not defined in this paper's own words; evidence base attached to checklist-item explanations — “In addition to the PRISMA Statement, a supporting Explanation and Elaboration document has been produced [18] following the style used for other reporting guidelines [19] – [21] . The process of completing this document included developing a large database of exemplars to highlight how best to report 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 face to face meetings and numerous iterations among several meeting participants, after which it was shared with the whole group for additional revisions and final approval. Finally, the group formed a dissemination subcommittee to help disseminate and implement PRISMA” | concepts[44] |
| concept | reporting an assessment of possible publication bias — not defined in this paper's own words; reported check treated as a marker of review thoroughness — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | concepts[45] |
| concept | thoroughness of the conduct of the systematic review — not defined in this paper's own words; review-conduct property indicated, but not proven, by bias-assessment reporting — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | concepts[46] |
| concept | results of systematic reviews — not defined in this paper's own words; review conclusions whose values can be altered by publication bias — “The quality of reporting of systematic reviews is still not optimal [22] – [27] . In a recent review of 300 systematic reviews, few authors reported assessing possible publication bias [22] , even though there is overwhelming evidence both for its existence [28] and its impact on the results of systematic reviews [29] . Even when the possibility of publication bias is assessed, there is no guarantee that systematic reviewers have assessed or interpreted it appropriately [30] . Although the absence of reporting such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication bias is likely to be a marker of the thoroughness of the conduct of the systematic review” | concepts[47] |
| concept | living document — not defined in this paper's own words; guideline designed for continued development from reader feedback — “Like any evidence-based endeavor, PRISMA is a living document. To this end we invite readers to comment on the revised version, particularly the new checklist and flow diagram, through the PRISMA Web site. We will use such information to inform PRISMA's continued development” | concepts[48] |
| confidence-interval CI | as written: confidence intervals — “Results of individual studies 20 For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group and (b) effect estimates and confidence intervals, ideally with a forest plot.” | content_tags.statistics[0] |
| mean μ | — “Reporting was generally poor; between one and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7).” | content_tags.statistics[1] |
| standard-deviation SD/σ | — “Reporting was generally poor; between one and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7).” | content_tags.statistics[2] |
| phenomenon | reporting quality of systematic reviews and meta-analyses — a second reading reaching the same value; recorded: reporting quality of systematic reviews and meta-analyses — “The quality of reporting of systematic reviews is still not optimal [22] – [27] .” | alternatives.phenomenon |
Full text — tagged
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Preferred Reportingterm Items for Systematic Reviewsterm·mth and Meta-Analyses: The PRISMAterm·mth Statement. PLoS Med 6(7): e1000097.
https://doi.org/10.1371/journal.pmed.1000097 Published: July 21, 2009 Copyright: © 2009 MoherpersName et al. This is an open-access articleterm·mth 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.
Funding: PRISMAterm·mth was funded by the Canadian Institutes of Health Research; Università di Modena e Reggio Emilia, Italy; Cancer Research UK; Clinical Evidenceterm·key BMJ Knowledge; the Cochrane Collaborationterm·dom; and GlaxoSmithKline, Canada. AL is funded, in part, through grants of the Italian Ministry of University (COFIN - PRIN 2002 prot. 2002061749 and COFIN - PRIN 2006 prot. 2006062298). DGA is funded by Cancer Research UK. DM is funded by a University of Ottawa Research Chair. None of the sponsors had any involvement in the planning, execution, or write-up of the PRISMAterm·mth documents. Additionally, no funder played a role in drafting the manuscript.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations: PRISMAterm·mth, Preferred Reportingterm Items for Systematic reviewsterm·mth and Meta-Analyses; QUOROMterm·mth, QU ality O f R eporting O f M eta-analyses Provenance: Not commissioned; externally peer reviewed. In order to encourage dissemination of the PRISMAterm·mth Statement, this articleterm·mth is freely accessible on the PLoS Medicine Web site ( http://medicine.plosjournals.org/ ) and will be also published in the Annals of Internal Medicine , BMJ , Journal of Clinical Epidemiology , and Open Medicine . The authors jointly hold the copyright of this articleterm·mth. For details on further use, see the PRISMAterm·mth Web site ( http://www.prisma-statement.org/ ).
Introduction Systematic reviewsterm·mth and meta-analyses have become increasingly important in health care. Clinicians read them to keep up to date with their field [1] , [2] , and they are often used as a starting point for developing clinical practice guidelines. Granting agencies may require a systematic reviewterm·mth to ensure there is justification for further research [3] , and some health care journals are moving in this direction [4] . As with all research, the value of a systematic reviewterm·mth depends on what was done, what was found, and the clarity of reportingterm. As with other publications, the reporting qualityterm of systematic reviewsterm·mth varies, limiting readers' ability to assess the strengths and weaknesses of those reviewsterm·key.
Several early studiesterm·mth evaluated the quality of reviewterm·key reports. In 1987, Mulrow examined 50 reviewterm·key articlesterm·mth published in four leading medical journals in 1985 and 1986 and found that none met all eight explicit scientific criteria, such as a quality assessment of included studiesterm·mth [5] . In 1987, Sacks and colleagues [6] evaluated the adequacy of reportingterm of 83 meta-analyses on 23 characteristics in six domains. Reportingterm was generally poor; between one and 14 characteristics were adequately reported (mean =term·stat 7.7; standard deviationterm·stat = 2.7). A 1996 update of this study found little improvement [7] .
In 1996, to address the suboptimal reportingterm of meta-analyses, an international group developed a guidance called the QUOROMterm·mth Statement ( QU ality O f R eporting O f M eta-analyses), which focused on the reportingterm of meta-analyses of randomized controlled trials [8] . In this articleterm·mth, we summarize a revision of these guidelines, renamed PRISMAterm·mth (Preferred Reportingterm Items for Systematic reviewsterm·mth and Meta-Analyses), which have been updated to address several conceptual and practical advances in the science of systematic reviewsterm·mth ( Box 1 ).
Box 1: Conceptual Issues in the Evolution from QUOROMterm·mth to PRISMAterm·mth Completing a Systematic Reviewterm·mth Is an Iterative Processterm The conduct of a systematic reviewterm depends heavily on the scope and quality of included studiesterm: thus systematicterm·key reviewers may need to modify their original reviewterm·key protocolterm·mth during its conductterm. Any systematic reviewterm·mth reportingterm guideline should recommend that such changes can be reported and explained without suggesting that they are inappropriate. The PRISMAterm·mth Statement (Items 5, 11, 16, and 23) acknowledges this iterative processterm. Aside from Cochrane reviewsterm·key, all of which should have a protocolterm·mth, only about 10% of systematicterm·key reviewers report working from a protocolterm·mth [22] . Without a protocolterm·mth that is publicly accessible, it is difficult to judge between appropriate and inappropriate modificationsterm.
Conductterm and Reportingterm Research Are Distinct Concepts This distinction is, however, less straightforward for systematic reviewsterm·mth than for assessments of the reportingterm of an individual study, because the reportingterm and conductterm of systematic reviewsterm·mth are, by nature, closely intertwined. For example, the failure of a systematic reviewterm·mth to report the assessment of the risk of biasterm·dom in included studiesterm·mth may be seen as a marker of poor conductterm, given the importance of this activity in the systematic reviewterm·mth process [37] .
Study-Levelterm Versus Outcome-Level Assessmentterm·def of Risk of Biasterm·dom For studiesterm·mth included in a systematic reviewterm·mth, a thorough assessment of the risk of biasterm·dom requires both a “study-levelterm” assessment (e.g., adequacy of allocation concealment) and, for some features, a newer approach called “outcome-levelterm” assessment. An outcome-level assessmentterm·def involves evaluating the reliability and validityterm of the data for each important outcome by determining the methods used to assess them in each individual study [38] . The quality of evidenceterm may differ across outcomes, even within a study, such as between a primary efficacy outcome, which is likely to be very carefully and systematically measured, and the assessment of serious harms [39] , which may rely on spontaneous reports by investigators. This information should be reported to allow an explicit assessment of the extent to which an estimate of effect is correct [38] .
Importance of Reporting Biasesterm·dom Different types of reporting biasesterm·dom may hamper the conductterm and interpretation of systematic reviewsterm·mth. Selective reporting of complete studiesterm (e.g., publication biasterm·dom) [28] as well as the more recently empirically demonstrated “outcome reporting biasterm·dom” within individual studiesterm·mth [40] , [41] should be considered by authors when conducting a systematic reviewterm·mth and reportingterm its results. Though the implications of these biases on the conductterm and reportingterm of systematic reviewsterm·mth themselves are unclear, some previous research has identified that selective outcome reportingterm may occur also in the context of systematic reviewsterm·mth [42] .
Terminology The terminology used to describe a systematic reviewterm·mth and meta-analysisterm·mth has evolved over time. One reason for changing the name from QUOROMterm·mth to PRISMAterm·mth was the desire to encompass both systematic reviewsterm·mth and meta-analyses. We have adopted the definitions used by the Cochrane Collaborationterm·dom [9] . A systematic reviewterm·mth is a reviewterm·key of a clearly formulated question that uses systematicterm·key and explicit methods to identify, select, and critically appraise relevant research, and to collect and analyze data from the studiesterm·mth that are included in the reviewterm·key. Statistical methods (meta-analysisterm·mth) may or may not be used to analyze and summarize the results of the included studiesterm·mth. Meta-analysisterm·mth refers to the use of statistical techniques in a systematic reviewterm·mth to integrate the results of included studiesterm·mth.
Developing the PRISMAterm·mth Statement A three-day meeting was held in Ottawa, Canada, in June 2005 with 29 participants, including reviewterm·key authors, methodologists, clinicians, medical editors, and a consumer. The objective of the Ottawa meeting was to revise and expand the QUOROMterm·mth checklistterm·mth and flow diagramterm·mth, as needed.
The executive committee completed the following tasks, prior to the meeting: a systematic reviewterm·mth of studiesterm·mth examining the quality of reportingterm of systematic reviewsterm·mth, and a comprehensive literature search to identify methodological and other articlesterm·mth that might inform the meeting, especially in relation to modifying checklistterm·mth items. An international survey of reviewterm·key authors, consumers, and groups commissioning or using systematic reviewsterm·mth and meta-analyses was completed, including the International Network of Agencies for Health Technology Assessment (INAHTA) and the Guidelines International Network (GIN). The survey aimed to ascertain views of QUOROMterm·mth, including the merits of the existing checklistterm·mth items. The results of these activities were presented during the meeting and are summarized on the PRISMAterm·mth Web site ( http://www.prisma-statement.org/ ).
Only items deemed essential were retained or added to the checklistterm·mth. Some additional items are nevertheless desirable, and reviewterm·key authors should include these, if relevant [10] . For example, it is useful to indicate whether the systematic reviewterm·mth is an update [11] of a previous reviewterm·key, and to describe any changes in procedures from those described in the original protocolterm·mth.
Shortly after the meeting a draft of the PRISMA checklistterm·def 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 checklistterm·mth was subsequently revised 11 times. The group approved the checklistterm·mth, flow diagramterm·mth, and this summary paper.
Although no direct evidenceterm·key was found to support retaining or adding some items, evidenceterm·key from other domains was believed to be relevant. For example, Item 5 asks authors to provide registrationterm·mth information about the systematic reviewterm·mth, including a registrationterm·mth number, if available. Although systematic review registrationterm is not yet widely available [12] , [13] , the participating journals of the International Committee of Medical Journal Editors (ICMJE) [14] now require all clinical trials to be registered in an effort to increase transparency and accountabilityterm [15] . Those aspects are also likely to benefit systematicterm·key reviewers, possibly reducing the risk of an excessive number of reviews addressing the same questionterm [16] , [17] and providing greater transparency when updating systematic reviewsterm·mth.
The PRISMAterm·mth Statement The PRISMAterm·mth Statement consists of a 27-item checklistterm ( Table 1 ; see also Text S1 for a downloadable Word template for researchers to re-use) and a four-phase flow diagramterm ( Figure 1 ; see also Figure S1 for a downloadable Word template for researchers to re-use). The aim of the PRISMAterm·mth Statement is to help authors improve the reportingterm of systematic reviewsterm·mth and meta-analyses. We have focused on randomized trials, but PRISMAterm·mth can also be used as a basis for reportingterm systematic reviewsterm·mth of other types of research, particularly evaluations of interventions. PRISMAterm·mth may also be useful for critical appraisalterm of published systematic reviewsterm·mth. However, the PRISMA checklistterm·def is not a quality assessment instrumentterm to gauge the quality of a systematic reviewterm·mth.
Download: PNG larger image TIFF original image Figure 1. Flow of information through the different phases of a systematic reviewterm·mth.
https://doi.org/10.1371/journal.pmed.1000097.g001 Download: PNG larger image TIFF original image Table 1. Checklistterm·mth of items to include when reportingterm a systematic reviewterm·mth or meta-analysisterm·mth.
https://doi.org/10.1371/journal.pmed.1000097.t001 From QUOROMterm·mth to PRISMAterm·mth The new PRISMA checklistterm·def differs in several respects from the QUOROMterm·mth checklistterm·mth, and the substantive specific changes are highlighted in Table 2 . Generally, the PRISMA checklistterm·def “decouples” several items present in the QUOROMterm·mth checklistterm·mth and, where applicable, several checklist itemsterm are linked to improve consistency across the systematic review reportterm.
Download: PNG larger image TIFF original image Table 2. Substantive specific changes between the QUOROMterm·mth checklistterm·mth and the PRISMA checklistterm·def (a tick indicates the presence of the topic in QUOROMterm·mth or PRISMAterm·mth).
https://doi.org/10.1371/journal.pmed.1000097.t002 The flow diagramterm·mth has also been modified. Before including studiesterm·mth and providing reasons for excluding others, the reviewterm·key team must first search the literature. This search results in recordsterm·mth. Once these recordsterm·mth have been screened and eligibility criteriaterm·mth applied, a smaller number of articlesterm·mth will remain. The number of included articlesterm·mth might be smaller (or larger) than the number of studiesterm·mth, because articlesterm·mth may report on multiple studiesterm·mth and results from a particular study may be published in several articlesterm·mth. To capture this information, the PRISMAterm·mth flow diagramterm·mth now requests information on these phases of the reviewterm·key process.
Endorsement The PRISMAterm·mth Statement should replace the QUOROMterm·mth Statement for those journals that have endorsed QUOROMterm·mth. We hope that other journals will support PRISMAterm·mth; they can do so by registering on the PRISMAterm·mth Web site. To underscore to authors, and others, the importance of transparentterm·key reportingterm of systematic reviewsterm·mth, we encourage supporting journals to reference the PRISMAterm·mth Statement and include the PRISMAterm·mth Web address in their Instructions to Authors. We also invite editorial organizations to consider endorsing PRISMAterm·mth and encourage authors to adhere to its principles.
The PRISMAterm·mth Explanation and Elaborationterm·mth Paper In addition to the PRISMAterm·mth Statement, a supporting Explanation and Elaborationterm·mth document has been produced [18] following the style used for other reportingterm guidelines [19] – [21] . The process of completing this document included developing a large database of exemplars to highlight how best to report each checklistterm·mth item, and identifying a comprehensive evidenceterm·key base to support the inclusion of each checklistterm·mth item. The Explanation and Elaborationterm·mth document was completed after several face to face meetings and numerous iterations among several meeting participants, after which it was shared with the whole group for additional revisions and final approval. Finally, the group formed a dissemination subcommittee to help disseminate and implement PRISMAterm·mth.
Discussion The quality of reportingterm of systematic reviewsterm·mth is still not optimal [22] – [27] . In a recent reviewterm·key of 300 systematic reviewsterm·mth, few authors reported assessing possible publication biasterm·dom [22] , even though there is overwhelming evidenceterm·key both for its existence [28] and its impact on the results of systematic reviewsterm [29] . Even when the possibility of publication biasterm·dom is assessed, there is no guarantee that systematicterm·key reviewers have assessed or interpreted it appropriately [30] . Although the absence of reportingterm such an assessment does not necessarily indicate that it was not done, reporting an assessment of possible publication biasterm is likely to be a marker of the thoroughness of the conduct of the systematic reviewterm.
Several approaches have been developed to conductterm systematic reviewsterm·mth on a broader array of questions. For example, systematic reviewsterm·mth are now conducted to investigate cost-effectiveness [31] , diagnostic [32] or prognostic questions [33] , genetic associations [34] , and policy making [35] . The general concepts and topics covered by PRISMAterm·mth are all relevant to any systematic reviewterm·mth, not just those whose objective is to summarize the benefits and harms of a health care intervention. However, some modifications of the checklistterm·mth items or flow diagramterm·mth will be necessary in particular circumstances. For example, assessing the risk of biasterm·dom is a key concept, but the items used to assess this in a diagnostic reviewterm·key are likely to focus on issues such as the spectrum of patients and the verification of disease status, which differ from reviewsterm·key of interventions. The flow diagramterm·mth will also need adjustments when reportingterm individual patient data meta-analysisterm·mth [36] .
We have developed an explanatory document [18] to increase the usefulness of PRISMAterm·mth. For each checklistterm·mth item, this document contains an example of good reportingterm, a rationale for its inclusionterm, and supporting evidenceterm, including references, whenever possible. We believe this document will also serve as a useful resource for those teaching systematic reviewterm·mth methodology. We encourage journals to include reference to the explanatory document in their Instructions to Authors.
Like any evidence-based endeavor, PRISMAterm·mth is a living documentterm. To this end we invite readers to comment on the revised version, particularly the new checklistterm·mth and flow diagramterm·mth, through the PRISMAterm·mth Web site. We will use such information to inform PRISMAterm·mth's continued development.
Supporting Information Figure S1.
Flow of information through the different phases of a systematic reviewterm·mth (downloadable template document for researchers to re-use).
https://doi.org/10.1371/journal.pmed.1000097.s001 (0.08 MB DOC) Text S1.
Checklistterm·mth of items to include when reportingterm a systematic reviewterm·mth or meta-analysisterm·mth (downloadable template document for researchers to re-use).
https://doi.org/10.1371/journal.pmed.1000097.s002 (0.04 MB DOC) Acknowledgments The following people contributed to the PRISMAterm·mth Statement: Doug AltmanpersName, DSc, Centre for Statistics in Medicine (Oxford, UK); Gerd Antes, PhD, University Hospital Freiburg (Freiburg, Germany); David Atkins, MD, MPH, Health Services Research and Development Service, Veterans Health Administration (Washington, D. C., US); Virginia Barbour, MRCP, DPhil, PLoS Medicine (Cambridge, UK); Nick Barrowman, PhD, Children's Hospital of Eastern Ontario (Ottawa, Canada); Jesse A. Berlin, ScD, Johnson & Johnson Pharmaceutical Research and Development (Titusville, New Jersey, US); Jocalyn Clark, PhD, PLoS Medicine (at the time of writing, BMJ , London, UK); Mike Clarke, PhD, UK Cochrane Centre (Oxford, UK) and School of Nursing and Midwifery, Trinity College (Dublin, Ireland); Deborah Cook, MD, Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University (Hamilton, Canada); Roberto D'Amico, PhD, Università di Modena e Reggio Emilia (Modena, Italy) and Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri (Milan, Italy); Jonathan J. Deeks, PhD, University of Birmingham (Birmingham, UK); P. J. Devereaux, MD, PhD, Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University (Hamilton, Canada); Kay Dickersin, PhD, Johns Hopkins Bloomberg School of Public Health (Baltimore, Maryland, US); Matthias Egger, MD, Department of Social and Preventive Medicine, University of Bern (Bern, Switzerland); Edzard Ernst, MD, PhD, FRCP, FRCP(Edin), Peninsula Medical School (Exeter, UK); Peter C. Gøtzsche, MD, MSc, The Nordic Cochrane Centre (Copenhagen, Denmark); Jeremy Grimshaw, MBChB, PhD, FRCFP, Ottawa Hospital Research Institute (Ottawa, Canada); Gordon Guyatt, MD, Departments of Medicine, Clinical Epidemiology and Biostatistics, McMaster University (Hamilton, Canada); Julian Higgins, PhD, MRC Biostatistics Unit (Cambridge, UK); John P. A. Ioannidis, MD, University of Ioannina Campus (Ioannina, Greece); Jos Kleijnen, MD, PhD, Kleijnen Systematic Reviewsterm·mth Ltd (York, UK) and School for Public Health and Primary Care (CAPHRI), University of Maastricht (Maastricht, Netherlands); Tom Lang, MA, Tom Lang Communications and Training (Davis, California, US); Alessandro LiberatipersName, MD, Università di Modena e Reggio Emilia (Modena, Italy) and Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri (Milan, Italy); Nicola Magrini, MD, NHS Centre for the Evaluation of the Effectiveness of Health Care – CeVEAS (Modena, Italy); David McNamee, PhD, The Lancet (London, UK); Lorenzo Moja, MD, MSc, Centro Cochrane Italiano, Istituto Ricerche Farmacologiche Mario Negri (Milan, Italy); David MoherpersName, PhD, Ottawa Methods Centre, Ottawa Hospital Research Institute (Ottawa, Canada); Cynthia Mulrow, MD, MSc, Annals of Internal Medicine (Philadelphia, Pennsylvania, US); Maryann Napoli, Center for Medical Consumers (New York, New York, US); Andy Oxman, MD, Norwegian Health Services Research Centre (Oslo, Norway); Ba' Pham, MMath, Toronto Health Economics and Technology Assessment Collaborative (Toronto, Canada) (at the time of the first meeting of the group, GlaxoSmithKline Canada, Mississauga, Canada); Drummond Rennie, MD, FRCP, FACP, University of California San Francisco (San Francisco, California, US); Margaret Sampson, MLIS, Children's Hospital of Eastern Ontario (Ottawa, Canada); Kenneth F. Schulz, PhD, MBA, Family Health International (Durham, North Carolina, US); Paul G. Shekelle, MD, PhD, Southern California Evidenceterm·key Based Practice Center (Santa Monica, California, US); Jennifer TetzlaffpersName, BSc, Ottawa Methods Centre, Ottawa Hospital Research Institute (Ottawa, Canada); David Tovey, FRCGP, The Cochrane Library, Cochrane Collaborationterm·dom (Oxford, UK) (at the time of the first meeting of the group, BMJ , London, UK); Peter Tugwell, MD, MSc, FRCPC, Institute of Population Health, University of Ottawa (Ottawa, Canada).
Author Contributions ICMJE criteria for authorship read and met: DM AL JT DGA. Wrote the first draft 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 evidenceterm·key base for PRISMAterm·mth, refining the checklistterm·mth, and drafting the manuscript: JT. Agree with the recommendations: DM AL JT DGA.
NOT THE PAPER'S TEXT. Added by this project on 2026-08-25: the table below was restored from the held scrape because the staged text did not contain it, and document order is therefore not the paper's. [TABLE 1 RESTORED 2026-08-25 by terminal-a from fulltext.html - the staged body said "consists of a 27-item checklist ( Table 1 )" and did not contain the table. APPENDED AT THE END so that no existing anchor offset moves; document order is therefore not the paper's. All 27 items verified present.] Table 1. Checklistterm·mth of items to include when reportingterm a systematic reviewterm·mth or meta-analysisterm·mth. Section/Topic # Checklistterm·mth Item Reported on Page # TITLE Title 1 Identify the report as a systematic reviewterm·mth, meta-analysisterm·mth, or both. ABSTRACT Structured summary 2 Provide a structured summary including, as applicable: background; objectives; data sources; study eligibility criteriaterm·mth, participants, and interventions; study appraisal and synthesis methods; results; limitations; conclusions and implications of key findings; systematic review registrationterm number. INTRODUCTION Rationale 3 Describe the rationale for the reviewterm·key in the context of what is already known. Objectives 4 Provide an explicit statement of questions being addressed with reference to participants, interventions, comparisons, outcomes, and study design (PICOS). METHODS Protocolterm·mth and registrationterm·mth 5 Indicate if a reviewterm·key protocolterm·mth exists, if and where it can be accessed (e.g., Web address), and, if available, provide registrationterm·mth information including registrationterm·mth number. Eligibility criteriaterm·mth 6 Specify study characteristics (e.g., PICOS, length of follow-up) and report characteristics (e.g., years considered, language, publication status) used as criteria for eligibility, giving rationale. Information sources 7 Describe all information sources (e.g., databases with dates of coverage, contact with study authors to identify additional studiesterm·mth) in the search and date last searched. Search 8 Present full electronic search strategy for at least one database, including any limits used, such that it could be repeated. Study selection 9 State the process for selecting studiesterm·mth (i.e., screening, eligibility, included in systematic reviewterm·mth, and, if applicable, included in the meta-analysisterm·mth). Data collection process 10 Describe method of data extraction from reports (e.g., piloted forms, independently, in duplicate) and any processes for obtaining and confirming data from investigators. Data items 11 List and define all variables for which data were sought (e.g., PICOS, funding sources) and any assumptions and simplifications made. Risk of biasterm·dom in individual studiesterm·mth 12 Describe methods used for assessing risk of biasterm·dom of individual studiesterm·mth (including specification of whether this was done at the study or outcome levelterm), and how this information is to be used in any data synthesis. Summary measures 13 State the principal summary measures (e.g., risk ratio, difference in means). Synthesis of results 14 Describe the methods of handling data and combining results of studiesterm·mth, if done, including measures of consistency (e.g., I 2) for each meta-analysisterm·mth. Risk of biasterm·dom across studiesterm·mth 15 Specify any assessment of risk of biasterm·dom that may affect the cumulative evidenceterm·key (e.g., publication biasterm·dom, selective reportingterm within studiesterm·mth). Additional analyses 16 Describe methods of additional analyses (e.g., sensitivity or subgroup analyses, meta-regression), if done, indicating which were pre-specified. RESULTS Study selection 17 Give numbers of studiesterm·mth screened, assessed for eligibility, and included in the reviewterm·key, with reasons for exclusions at each stage, ideally with a flow diagramterm·mth. Study characteristics 18 For each study, present characteristics for which data were extracted (e.g., study size, PICOS, follow-up period) and provide the citations. Risk of biasterm·dom within studiesterm·mth 19 Present data on risk of biasterm·dom of each study and, if available, any outcome-level assessmentterm·def (see Item 12). Results of individual studiesterm·mth 20 For all outcomes considered (benefits or harms), present, for each study: (a) simple summary data for each intervention group and (b) effect estimates and confidence intervalsterm·stat, ideally with a forest plot. Synthesis of results 21 Present results of each meta-analysisterm·mth done, including confidence intervalsterm·stat and measures of consistency. Risk of biasterm·dom across studiesterm·mth 22 Present results of any assessment of risk of biasterm·dom across studiesterm·mth (see Item 15). Additional analysis 23 Give results of additional analyses, if done (e.g., sensitivity or subgroup analyses, meta-regression [see Item 16]). DISCUSSION Summary of evidenceterm·key 24 Summarize the main findings including the strength of evidenceterm·key for each main outcome; consider their relevance to key groups (e.g., health care providers, users, and policy makers). Limitations 25 Discuss limitations at study and outcome levelterm (e.g., risk of biasterm·dom), and at reviewterm·key level (e.g., incomplete retrieval of identified research, reporting biasterm·dom). Conclusions 26 Provide a general interpretation of the results in the context of other evidenceterm·key, and implications for future research. FUNDING Funding 27 Describe sources of funding for the systematic reviewterm·mth and other support (e.g., supply of data); role of funders for the systematic reviewterm·mth. doi:10.1371/journal.pmed.1000097.t001