Article type
Year
Abstract
Introduction/Objective: To determine whether blinding readers of meta-analyses to identifying information in original papers has an effect on the results of the meta-analyses.
Methods: Readers were randomly assigned to perform meta-analyses under either blinded or unblinded conditions. Papers given to blinded readers were electronically scanned from published papers, reprinted in a common type face, and stripped of identifying information about authors, institutions, journals of publication, and treatment assignments. Five previously published meta-analyses were chosen at random, and we applied the original inclusion and exclusion criteria for the published studies. The Mantel-Haenszel summary odds ratio was calculated for each meta-analysis separately for blinded and unblinded conditions and compared using inverse-variance-weighted, least-squares regression, taking the pairing of observations into account.
Results: The summary odds ratio for the five, blinded meta-analyses was 0.63 (95% Confidence Interval (CI): 0.57, 0.69), compared with 0.64 (0.57, 0.72) for the unblinded meta-analyses (p = 0.39 for the blinded versus unblinded comparision). The blinding process was extremely time-consuming.
Discussion: Blinding readers to identifying information in original papers appears to have little effect on the summary odds ratio calculated for the meta-analysis, and it is time-consuming. Therefore, we recommend that blinding not be used when meta-analyses are performed.
Methods: Readers were randomly assigned to perform meta-analyses under either blinded or unblinded conditions. Papers given to blinded readers were electronically scanned from published papers, reprinted in a common type face, and stripped of identifying information about authors, institutions, journals of publication, and treatment assignments. Five previously published meta-analyses were chosen at random, and we applied the original inclusion and exclusion criteria for the published studies. The Mantel-Haenszel summary odds ratio was calculated for each meta-analysis separately for blinded and unblinded conditions and compared using inverse-variance-weighted, least-squares regression, taking the pairing of observations into account.
Results: The summary odds ratio for the five, blinded meta-analyses was 0.63 (95% Confidence Interval (CI): 0.57, 0.69), compared with 0.64 (0.57, 0.72) for the unblinded meta-analyses (p = 0.39 for the blinded versus unblinded comparision). The blinding process was extremely time-consuming.
Discussion: Blinding readers to identifying information in original papers appears to have little effect on the summary odds ratio calculated for the meta-analysis, and it is time-consuming. Therefore, we recommend that blinding not be used when meta-analyses are performed.