BMJ : British medical journal
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Objective To evaluate the impact of searching clinical trial registries in systematic reviews. Design Methodological systematic review and reanalyses of meta-analyses. Data sources Medline was searched to identify systematic reviews of randomised controlled trials (RCTs) assessing pharmaceutical treatments published between June 2014 and January 2015. ⋯ However, none of the changes to summary effect estimates led to a qualitative change in the interpretation of the results once the new trials were added. Conclusions Trial registries are an important source for identifying additional RCTs. The additional number of RCTs and patients included if a search were performed varied across systematic reviews.