Center-specific causal inference with multicenter trials: reinterpreting trial evidence in the context of each participating center

Understand

In multicenter randomized trials, when effect modifiers have a different distribution across centers, comparisons between treatment groups that average over centers may not apply to any of the populations underlying the individual centers.

• Here, we describe methods for reinterpreting the evidence produced by a multicenter trial in the context of the population underlying each center.
• We describe how to identify center-specific effects under identifiability conditions that are largely supported by the study design and when associations between center membership and the outcome may be present, given baseline covariates and treatment ("center-outcome associations").
• We then consider an additional condition of no center-outcome associations given baseline covariates and treatment.