Table 1.

Summary of risk of bias domains and criteria for low risk designation

Risk of bias domain	Low risk of bias designation^a
Recruitment strategy	Protocols for recruitment and inclusion/exclusion criteria applied similarly across study groups
Blinding	Knowledge of the exposure ensured when assessing outcome, or judgement that outcome measurement not likely to be influenced by lack of blinding
Exposure assessment	Confidence in the accuracy of the exposure assessment methods that minimizes exposure misclassification, i.e., validity and reliability measures specified for monitoring and modeling
Confounding	All five important potential confounders pre-specified by reviewers are accounted for (i.e., matched, stratified, multivariate analysis or otherwise statistically controlled for)
Incomplete outcome	No missing outcome data, balanced attrition across groups, or for continuous outcome data, plausible effect size among missing outcomes not enough to have a relevant impact on the observed effect size
Selective outcome reporting	All pre-specified outcomes outlined in the protocol, methods, abstract, and/or introduction reported in the pre-specified way
Conflicts of Interest	The study did not receive support from a company, study author, or other entity having a financial interest in the outcome of the study
Other bias	The study appears to be free of other sources of bias

The complete criteria for determining risk of bias designations for individual studies are provided in Supplemental Material Table S3, “Instructions for Making Risk of Bias Determinations.”