• Lisa Hartling, Michele P Hamm, Andrea Milne, Ben Vandermeer, P Lina Santaguida, Mohammed Ansari, Alexander Tsertsvadze, Susanne Hempel, Paul Shekelle, and Donna M Dryden.
• Department of Pediatrics, Alberta Research Centre for Health Evidence and the University of Alberta Evidence-based Practice Center, University of Alberta, 4-472 Edmonton Clinic Health Academy, 11405-87 Avenue, Edmonton, Alberta, Canada. hartling@ualberta.ca
• J Clin Epidemiol. 2013 Sep 1;66(9):973-81.

ObjectivesTo assess the reliability of the Cochrane Risk of Bias (ROB) tool between individual raters and across consensus agreements of pairs of reviewers and examine the impact of study-level factors on reliability.Study Design And SettingTwo reviewers assessed risk of bias for 154 randomized controlled trials (RCTs). For 30 RCTs, two reviewers from each of four centers assessed risk of bias and reached consensus. We assessed interrater agreement using kappas and the impact of study-level factors through subgroup analyses.ResultsReliability between two reviewers was fair for most domains (κ=0.24-0.37), except sequence generation (κ=0.79, substantial). Reliability results across reviewer pairs: sequence generation, moderate (κ=0.60); allocation concealment and "other sources of bias," fair (κ=0.37-0.27); and other domains, slight (κ=0.05-0.09). Reliability was influenced by the nature of the outcome, nature of the intervention, study design, trial hypothesis, and funding source. Variability resulted from different interpretation of the tool rather than different information identified in the study reports.ConclusionLow agreement has implications for interpreting systematic reviews. These findings suggest the need for detailed guidance in assessing the risk of bias.Copyright © 2013 Elsevier Inc. All rights reserved.

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