Journal
JOURNAL OF CLINICAL EPIDEMIOLOGY
Volume 68, Issue 11, Pages 1282-1291Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.jclinepi.2015.02.009
Keywords
Systematic review; Meta-analysis; Randomized controlled trials; Reporting; Bias; Research methodology
Funding
- Australian Postgraduate Award
- NHMRC Australian Public Health Fellowship [1072366]
- MRC [MR/K025643/1] Funding Source: UKRI
- Medical Research Council [MR/K025643/1] Funding Source: researchfish
- National Institute for Health Research [NF-SI-0514-10114] Funding Source: researchfish
- National Health and Medical Research Council of Australia [1072366] Funding Source: NHMRC
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Objectives: To investigate how often systematic reviewers encounter multiple trial effect estimates that are available for inclusion in a particular meta-analysis (multiplicity of results) and the methods they use to select effect estimates. Study Design and Setting: We randomly sampled Cochrane and MEDLINE-indexed non-Cochrane reviews published between January 2010 and January 2012. The first presented meta-analysis of an effect measure for a continuous outcome in each review was identified, and methods to select results to include in this meta-analysis were extracted from review protocols and reviews. All effect estimates that were available for inclusion in the meta-analyses were extracted from trial reports. Results: We examined 44 reviews. Multiplicity of results was common, occurring in 49% of trial reports (n = 210). Prespecification of decision rules to select results from multiple measurement scales and intervention/control groups (in multi-arm trials) was uncommon (19% and 14% of 21 review protocols, respectively). Overall, 70% of reviews included at least one randomized controlled trial with multiplicity of results, but this occurred less frequently in reviews with a protocol (risk difference, -25%; 95% confidence interval: -52%, 1%). Conclusion: Systematic reviewers are likely to encounter multiplicity of results in the included trials. We recommend that systematic reviewers always consider predefining methods to select results to include in meta-analyses. Methods focusing on selection of measurement scales and how to deal with multi-arm trials would be most valuable. (C) 2015 Elsevier Inc. All rights reserved.
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