CYP2C19 and clopidogrel response: more than validation in the real world.

Electronic health records (EHRs) coupled to DNA biobanks are potentially powerful but untested resources for pharmacogenomic discoveries. As described in this issue, Delaney and co-workers validated the use of EHRs by demonstrating that loss-of-function CYP2C19*2 was associated with poorer cardiovascular outcomes in clopidogrel-treated patients with an effect size similar to that reported in more controlled clinical trials. Whether studies from real-world EHR-biobanks will supplant randomized clinical trials to provide a sufficient evidence base to change practice is less certain.