A meta-analysis of 9 clopidogrel studies with a combined 10 000 participants—comprising mostly PCI patients, with over half being treated for an acute coronary syndrome—found that carriers of reduced-function CYP2C19 alleles suffered a 57% increase in risk of cardiovascular death, myocardial infarction, or ischemic stroke compared with noncarriers.20 The increased risk affected carriers of 2 reduced-function CYP2C19 alleles (76% increase) as well as carriers of 1 reduced-function CYP2C19 allele (55% increase). This evidence concerns the gene CYP2C19 and ischemic stroke.