This guidance represents FDA’s current thinking on adjusting for covariates in the statistical analysis of randomized clinical trials in drug development programs. This guidance provides recommendations for the use of covariates in the analysis of randomized, parallel group clinical trials that are applicable to both superiority trials and noninferiority trials. The main focus of the guidance is on the use of prognostic baseline factors to improve precision for estimating treatment effects rather than the use of predictive biomarkers to identify groups more likely to benefit from treatment. This guidance does not address use of covariates to control for confounding variables in non-randomized trials or the use of covariate adjustment for analyzing longitudinal repeated measures data.

This guidance revises the draft guidance for industry Adjusting for Covariates in Randomized Clinical Trials for Drugs and Biologics with Continuous Outcomes issued in April 2019. This revision provides more detailed recommendations for the use of linear models for covariate adjustment and also includes recommendations for covariate adjustment using nonlinear models.