(143) Extending Treatment Effects from a Randomized Trial Using Observational Data

Publication Number: 474

Background: To increase confidence in the use of observational data for extending inferences from randomized trials, one can first benchmark. That is, demonstrate the observational analysis can replicate an index trial’s findings, before using the observational data to estimate what the trial could not.

Objectives: To benchmark an observational study designed to ask the questions to the TASTE trial against results from the TASTE trial itself. Then, if benchmarking is successful, use the observational data to extend the inferences made in the trial.

Methods: We use Swedish registry data to emulate a target trial similar to the TASTE randomized trial, which found no difference in the risk of death or myocardial infarction by 1 year with or without thrombus aspiration among individuals with ST-elevation myocardial infarction. We benchmark the emulation against the trial at 1 year, then extend the emulation’s follow-up to 3 years and estimate effects in subpopulations underrepresented in the trial.

Results: Like TASTE, the observational analysis found no differences in risk of outcomes by 1 year between groups (risk difference 0.7 (-0.7,2.0) and -0.2 (-1.3,1.0) for death and myocardial infarction respectively), so benchmarking was considered successful. We additionally show no difference in risk of death or myocardial infarction by 3 years, or within subpopulations by 1 year.

Conclusions: Benchmarking before using observational data to extend treatment effects from a randomized trial allows us to understand if the observational data can be trusted to deliver valid estimates of treatment effects.