Background: CYP2C19*2 polymorphism is related to metabolizer phenotypes resulting in reduced effectiveness in converting the antiplatelet drug clopidogrel to active drug. An association of the genotype itself with adverse outcomes is discussed. We investigated the prognostic value of carriage of the CYP2C19*2 allele in a high risk group of patients with prevalent coronary heart disease (CHD) at baseline during long-term follow-up under conditions of routine clinical care.
Methods: In n=1050 patients with stable CHD at baseline genotyping of CYP2C19 allele *2 (rs4244285; 681G>A) was performed. The Cox-proportional hazards model was employed to investigate the association of CYPC19*2 allele status with cardiovascular disease (CVD) events during eight year follow-up. The analysis was also performed in patients who did not take clopidogrel or ticlopidin.
Results: Only the very few patients homozygous for a loss-of-function variant of CYP2C19, allele *2 (2.6%), had a statistically significantly higher incidence rate for secondary CVD events during long-term follow-up than wild-type carriers (50.8 versus 21.5 per 1000 patients years; rate for heterozygous carries 17.2 per 1000 patient years). The hazard ratio after adjustment for covariates compared to the wild-type carriers was 2.59 (95% confidence interval (CI) 1.27-5.28) and 0.80 (95% CI 0.52-1.23) for homozygous and heterozygous allele carriers, respectively.
Conclusions: In this medium-size group of patients with stable CHD homozygous carriers of the loss-of-function allele CYP2C19*2 were at increased risk for subsequent CVD events during 8 year follow-up independent of other risk factors. As only few patients carried the homozygous loss-of-function variant and we found overall no evidence for improved clinical utility, a benefit of genotyping in this patient population seems unlikely.