The impact of blinding on trial results: A systematic review and meta‐analysis

Abstract

Abstract Background Blinding?the concealment of the arm to which participants have been randomized?is an important consideration for assessing the risk of bias of randomized trials. A growing body of evidence has, however, yielded inconsistent results on whether trials without blinding produce biased findings. Objective To conduct a systematic review and meta-analysis of the evidence addressing whether trials with and without blinding produce different results. Methods We searched MEDLINE, EMBASE, Cochrane Reviews, JBI EBP, and Web of Science, from inception to May 2022, for studies comparing the results of trials with and without blinding. Pairs of reviewers, working independently and in duplicate, reviewed search results for eligible studies and extracted data. We pooled the results of studies comparing trials with and without blinding of patients, healthcare providers/investigators, and outcome assessors/adjudicators using frequentist random-effects meta-analyses. We coded study results such that a ratio of odds ratio?