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

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

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.

Several early studies evaluated the quality of review reports. In 1987, Mulrow examined 50 review articles published in 4 leading medical journals in 1985 and 1986 and found that none met all 8 explicit scientific criteria, such as a quality assessment of included studies.5 In 1987, Sacks and colleagues6 evaluated the adequacy of reporting of 83 meta-analyses on 23 characteristics in 6 domains. Reporting was generally poor; between 1 and 14 characteristics were adequately reported (mean = 7.7; standard deviation = 2.7). A 1996 update of this study found little improvement.7

In 1996, to address the suboptimal reporting of meta-analyses, an international group developed a guidance called the QUOROM Statement (QUality Of Reporting Of Meta-analyses), which focused on the reporting of meta-analyses of randomized controlled trials.8 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).



Box 1

Conceptual issues in the evolution from QUOROM to PRISMA

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

Objective: Funnel plots (plots of effect estimates against sample size) may be useful to detect bias in meta-analyses that were later contradicted by large trials. We examined whether a simple test of asymmetry of funnel plots predicts discordance of results when meta-analyses are compared to large trials, and we assessed the prevalence of bias in published meta-analyses. Design: Medline search to identify pairs consisting of a meta-analysis and a single large trial (concordance of results was assumed if effects were in the same direction and the meta-analytic estimate was within 30% of the trial); analysis of funnel plots from 37 meta-analyses identified from a hand search of four leading general medicine journals 1993-6 and 38 meta-analyses from the second 1996 issue of the Cochrane Database of Systematic Reviews . Main outcome measure: Degree of funnel plot asymmetry as measured by the intercept from regression of standard normal deviates against precision. Results: In the eight pairs of meta-analysis and large trial that were identified (five from cardiovascular medicine, one from diabetic medicine, one from geriatric medicine, one from perinatal medicine) there were four concordant and four discordant pairs. In all cases discordance was due to meta-analyses showing larger effects. Funnel plot asymmetry was present in three out of four discordant pairs but in none of concordant pairs. In 14 (38%) journal meta-analyses and 5 (13%) Cochrane reviews, funnel plot asymmetry indicated that there was bias. Conclusions: A simple analysis of funnel plots provides a useful test for the likely presence of bias in meta-analyses, but as the capacity to detect bias will be limited when meta-analyses are based on a limited number of small trials the results from such analyses should be treated with considerable caution. Key messages Systematic reviews of randomised trials are the best strategy for appraising evidence; however, the findings of some meta-analyses were later contradicted by large trials Funnel plots, plots of the trials9 effect estimates against sample size, are skewed and asymmetrical in the presence of publication bias and other biases Funnel plot asymmetry, measured by regression analysis, predicts discordance of results when meta-analyses are compared with single large trials Funnel plot asymmetry was found in 38% of meta-analyses published in leading general medicine journals and in 13% of reviews from the Cochrane Database of Systematic Reviews Critical examination of systematic reviews for publication and related biases should be considered a routine procedure

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Bias in meta-analysis detected by a simple, graphical test

Systematic review and meta-analysis

Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement

The EU Clinical Trials Directive has been heavily criticised for being bureaucratic, confusing, and leading to a decline in the number of trials conducted in Europe. Although new proposals for regulation are much better, Peter Gotzsche argues improvements are still needed for patient safety, rational use of drugs, and research planning

https://www.bmj.com/content/bmj/345/bmj.e8522.full.pdf

Deficiencies in proposed new EU regulation of clinical trials

Unreliable analysis of placebo analgesia in trials of placebo pain mechanisms.

/pdf/declaracion-de-la-iniciativa-stobe-strengthening-the-4attfazhyr.pdf

Declaración de la Iniciativa STOBE (Strengthening the Reporting of Observational Studies in Epidemiology): directrices para informar sobre los estudios observacionales

Biases in estimates of overdetection due to mammography screening.

OBJECTIVES—To study whether the reporting of clinical outcomes in arthritis trials measured on ordinal and interval scales is adequate in relation to meta-analysis.
METHODS—Systematic review of randomised trials of non-steroidal anti-inflammatory drugs in patients with rheumatoid arthritis. Optimal reporting was defined as data in the original ordered categories for global evaluation and pain, and as mean and SD for number of tender joints and grip strength, and if a visual analogue scale had been used to measure pain.
RESULTS—A total of 144 trials were included. The median sample size was 60 patients. The quality of the reporting increased over time for three of the four variables. Global evaluation was optimally reported in 52 of the 127 trials (41%) in which it was recorded. Pain was optimally reported in 27 of 98 trials (28%), number of tender joints in 41 of 123 trials (33%), and grip strength in 34 of 124 trials (27%). Even if rather broad criteria are adopted, only about half of the data were reported in a potentially useful way for a meta-analysis.
CONCLUSIONS—Arthritis trials have been reported inadequately in relation to meta-analysis. As most trials are underpowered, meta-analysis is indispensable and the deficit therefore needs urgent improvement. Investigators should specify a priori what constitutes an important treatment effect and report numbers of patients improved.

https://ard.bmj.com/content/annrheumdis/60/4/349.full.pdf

Peter C Gøtzsche

Papers

Deficiencies in proposed new EU regulation of clinical trials

Unreliable analysis of placebo analgesia in trials of placebo pain mechanisms.

Declaración de la Iniciativa STOBE (Strengthening the Reporting of Observational Studies in Epidemiology): directrices para informar sobre los estudios observacionales

Biases in estimates of overdetection due to mammography screening.

Reporting of outcomes in arthritis trials measured on ordinal and interval scales is inadequate in relation to meta-analysis.