Investigating Real-World Clopidogrel Pharmacogenetics in Stroke Using a Bioresource Linked to Electronic Medical Records

Clopidogrel efficacy is influenced by genetic variation of CYP2C19, however few studies have considered stroke patients. We used electronic medical records (EMR) linked to a bioresource to examine real-world implications of clopidogrel pharmacogenetics in stroke. Patients hospitalized for any arterial thrombo-occlusive event (ATO) who subsequently redeemed clopidogrel prescriptions in the community were entered into the study (n=651). During 24 months follow-up the primary endpoint of recurrent ATO or death occurred in 299 (46%) patients. CYP2C19*2 loss-of-function allele carriers had an increased risk, hazard ratio (HR) 1.29 (95% confidence interval 1.04-1.59, P=0.019). In the ischemic stroke subgroup (n=94) the estimate of risk was greater (HR 2.23, 95% confidence interval 1.17-4.24, P=0.015) further supported by a meta-analysis of available studies. In conclusion, we have demonstrated the clinical impact of CYP2C19*2 on clopidogrel efficacy using a purely EMR approach. This suggests that the risk in the ischemic stroke population may be particularly high.