Recommendations for assessing the risk of bias in systematic reviews of health care interventions
OBJECTIVE: Risk-of-bias assessment is a central component of systematic reviews but little conclusive empirical evidence exists on the validity of such assessments. In the context of such uncertainty, we present pragmatic recommendations that promote transparency and reproducibility in processes, address methodological advances in the risk-of-bias assessment, and can be applied consistently across review topics.
STUDY DESIGN: Epidemiological study design principles; available empirical evidence, risk-of-bias tools, and guidance; and workgroup consensus RESULTS: We developed recommendations for assessing the risk of bias of studies of health care interventions specific to framing the focus and scope of risk-of-bias assessment; selecting risk of bias categories; choosing assessment instruments; and conducting, analyzing, and presenting results of risk-of-bias assessments. Key recommendations include transparency and reproducibility of judgments, separating risk of bias from other constructs such as applicability and precision, and evaluating risk of bias per outcome. We recommend against certain past practices, such as focusing on reporting quality, relying solely on study design or numerical quality scores, and automatically downgrading for industry sponsorship.
CONCLUSION: Risk-of-bias assessment remains a challenging but essential step in systematic reviews. We presented standards to promote transparency of judgments.