Objective To evaluate the platelet inhibition with VerifyNow-P2Y12 assay in patients under regular maintenance dose of Clopidogrel, and explore the clinical characteristics of Clopidogrel non-responsive and its predicting factors.
Methods A total of 99 patients undergone PCI procedure and were receiving Clopidogrel in regular maintenance dose for at least 1 week were enrolled. Platelet reactivity, including Baseline, P2Y12 Reaction Unit (PRU), and platelet inhibition rate were measured with VeifyNow-P1Y12 assay (Accumetrics Inc., San Diego, CA, USA). The dosage of anti-platelet drugs, combination with any other drugs, clinical characters in baseline of all the enrolled patients was recorded in detail for evaluation. PRU ≤ 240 was used as cut-off to indentify Clopidogrel responsive and Clopidogrel non-responsive patients. In the non-responsive group, patients were further separated into 3 sub-groups (types) according to the baseline and platelet inhibition rate. Type I has high baseline, high inhibition rate, represents false non-responsiveness, Type II has low inhibition rate, represents true non-responsive, and Type III is combination.
Results In this study, 48 of 99 patients were found to be Clopidogrel non-responsive (48.5%). The ratio of Type I, Type II and Type III in the non-responsive group were 9(9.1%), 27(27.3%), and 12(12.1%), respectively. Female’s baseline value of platelet value was significantly higher than male’s (p < 0.01), number of females with high PRU also is high than males (p < 0.01), so female was a predict factor for Type I non-responsiveness (OR = 6.5, 95% CI 2.295 ∼ 18.407, P < 0.01). BMI > 24 kg/m2 show significant correlation with Clopidorgrel non-responsive (p < 0.05), and may be regarded as a predict factor for Type II non-responsiveness (OR = 3.207, 95% CI 1.375 ∼ 7.485, P < 0.01). Age, Hypertension, Diabetics, smoking, hyperlipidemia, CRP, and Pantoprazole do not show significant correlation with baseline and platelet inhibition rate.
Conclusions With VerifyNow-P2Y12 assay, Clopidogrel non-responsive Type I is caused by high baseline, and female patients is an independent predicting factor; Clopidogrel non-responsive Type II has true low platelet inhibition rate, related to the low effectiveness of Clopidogrel, high body weight may have some effects. Clopidogrel non-responsive Type III can have the characters of both type I and type II. Age, Hypertension, Diabetics, smoking, hyperlipidemia, CRP, and Pantoprazole do not relate to Clopidogrel non-responsive.