CYP2C19 and ischemic stroke: Indeed, results of a large meta-analysis of 15 studies [16], which has been published in 2017, highlighted that reduced-function CYP2C19 allele carriers have an increased risk of stroke following TIA or ischemic stroke when treated with clopidogrel compared to non-carriers (RR: 1.92, 95%CI: 1.57–2.35, P < 0.00001).