CYP2C19 and chronic kidney disease: [27, 28] As previously published, we found higher levels of adenosine diphosphate inducible platelet aggregation by light transmission aggregometry in clopidogrel-treated patients carrying loss-of-function polymorphisms of CYP2C19 [29], in those aged 75 years or older [30], in those concomitantly receiving calcium channel blockers [31], and in those with chronic kidney disease [32] (all p < 0.05).