Intended for healthcare professionals


The problem of duplicate systematic reviews

BMJ 2013; 347 doi: (Published 14 August 2013) Cite this as: BMJ 2013;347:f5040
  1. David Moher, senior scientist
  1. 1Clinical Epidemiology Program, Ottawa Hospital Research Institute, Ottawa Hospital, Ottawa, Canada ON K1H 8L6
  1. dmoher{at}

Systematic reviewers should identify existing reviews as a compulsory first step

Systematic reviews occupy a central position in evidence based medicine. They are the starting point of a well developed practice guideline. Some funders of randomised trials ask investigators for a strong rationale for their proposed trial, indicating that the best evidence is likely to be a well conducted and completely reported systematic review.1 These reasons, and others, probably explain the popularity and publication trajectory of systematic reviews.2 Does this translate into duplication of effort and waste? In a linked paper (doi:10.1136/bmj.f4501), using sound methodology and complete and transparent reporting, Siontis and colleagues examined this question.3

Having selected 73 meta-analyses published during 2010, the authors identified two thirds of them as having at least one overlapping meta-analysis. The good news is that duplication does not seem to have been a major problem. The authors report a median of two overlapping meta-analyses per topic. However, for several clinical topics there were multiple duplicates, and in 17 instances at least one author was involved in more than one overlapping meta-analysis. These findings provide another …

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