Some Cochrane risk of bias items are not important in osteoarthritis trials: A meta-epidemiological study based on Cochrane reviews

Publication date: Available online 6 December 2017
Source:Journal of Clinical Epidemiology
Author(s): Julie Bolvig, Carsten B. Juhl, Isabelle Boutron, Peter Tugwell, Elizabeth A.T. Ghogomu, Jordi Pardo Pardo, Tamara Rader, George A. Wells, Alain Mayhew, Lara Maxwell, Hans Lund, Henning Bliddal, Robin Christensen
ObjectiveTo evaluate the impact of bias-related study characteristics on treatment effects in osteoarthritis (OA) trials.Study designBased on OA trials included in Cochrane reviews the impact of study characteristics on treatment effect estimates were evaluated. Characteristics included items of the risk of bias tool (RoB), trial size, single vs multi-site, and source of funding. Effect sizes were calculated as standardized mean differences (SMDs). Meta-regression was performed to identify "relevant study-level covariates" that decreases the between-study variance (τˆ²).ResultsTwenty reviews including 126 OA trials with a high degree of heterogeneity was included (τˆ²=0.1247). Among RoB domains only patient blinding had an impact on the results (reducing heterogeneity according to τˆ² <7%). Inadequate blinding of patients yielded larger effects (SMDDifference = 0.15; 95% CI: 0.11 to 0.29, P=0.035). The most important study characteristic was trial size (heterogeneity reduced by 25%), with small trials reporting larger effects (SMDDifference = 0.29; 95% CI: 0.16 to 0.42, P<0.001).ConclusionIn musculoskeletal reviews addressing pain, all the items included in the Cochrane risk of bias tool might not be equally important. OA trial results may be affected by bias constructs that are not yet fully elucidated.



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