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Association Between Risk-of-Bias Assessments and Results of Randomized Trials in Cochrane Reviews: the ROBES Meta-Epidemiologic Study

Savović, J; Turner, RM; Mawdsley, D; Jones, HE; Beynon, R; Higgins, JPT; Sterne, JAC; (2017) Association Between Risk-of-Bias Assessments and Results of Randomized Trials in Cochrane Reviews: the ROBES Meta-Epidemiologic Study. American Journal of Epidemiology 10.1093/aje/kwx344. (In press). Green open access

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Abstract

Flaws in trial design may lead to biased intervention effect estimates and increases in between-trial heterogeneity. Empirical evidence suggests that these problems are greatest for estimates based on subjectively assessed outcomes. We extracted risk-of-bias judgements (for sequence generation, allocation concealment, blinding and incomplete data) from a large collection of meta-analyses published in issue 4, 2011 of the Cochrane Library. We classified outcome measures as mortality, other objective or subjective, and estimated associations of bias judgements with intervention effect estimates using Bayesian hierarchical models. Among 2443 trials in 228 meta-analyses, intervention effect estimates were on average exaggerated in trials with high or unclear risk-of-bias judgements (versus low) for sequence generation (ratio of odds ratio 0.91 [95% credible interval 0.86, 0.98]), allocation concealment (0.92 [0.86-0.98]) and blinding (0.87 [0.80, 0.93]). In contrast to previous work, we did not observe consistently different bias for subjective outcomes compared to mortality. However, we did find an increase in between-trial heterogeneity associated with lack of blinding in meta-analyses with subjective outcomes. Inconsistency in criteria for risk-of-bias judgments applied by individual reviewers is a likely limitation of routinely collected bias assessments. Inadequate randomization and lack of blinding lead to exaggeration of intervention effect estimates in trials.

Type: Article
Title: Association Between Risk-of-Bias Assessments and Results of Randomized Trials in Cochrane Reviews: the ROBES Meta-Epidemiologic Study
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/aje/kwx344
Publisher version: http://doi.org/10.1093/aje/kwx344
Language: English
Additional information: Copyright © The Author(s) 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Keywords: meta-analysis, blinding, randomization, allocation concealment, missing data, bias, trials
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Inst of Clinical Trials and Methodology
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Inst of Clinical Trials and Methodology > MRC Clinical Trials Unit at UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10039948
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