OBJECTIVETo evaluate the platelet inhibition efficacy in patients under regular maintenance dose of clopidogrel by VerifyNow-P2Y12 assay and explore the clinical characteristics of clopidogrel non-responders and related predicting factors.

METHODSA total of 99 patients underwent percutaneous coronary intervention procedure and 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-P2Y12 assay. The dosage of anti-platelet drugs, combination with any other drugs, clinical characters in baseline of all enrolled patients were analyzed. PRU ≤ 240 was used as cut-off to identify clopidogrel responder and clopidogrel non-responder. In the non-responder group, patients were further separated into 3 sub-groups (types) according to the baseline and platelet inhibition rate: type I with high baseline, high inhibition rate, representing false non-responder; type II with low inhibition rate, representing true non-responder and type III mixed type.

RESULTSIn this study, 48 of 99 patients were found to be clopidogrel non-responder (48.5%). The ratio of type I, type II and type III in the non-responder group was 9.1% (n = 9), 27.3% (n = 27), and 12.1% (n = 12), respectively. Baseline platelet value in female patients was significantly higher than in males (P < 0.01), number of females with high PRU also is higher than males (P < 0.01), female gender was a predict factor for type I non-responder (OR = 6.5, 95%CI 2.295 - 18.407, P < 0.01). BMI > 24 kg/m(2) was a risk factor for clopidogrel non-responder (P < 0.05), and may be regarded as a predict factor for type II non-responder (OR = 3.207, 95%CI 1.375 - 7.485, P < 0.01). Age, hypertension, diabetics, smoking, hyperlipidemia, CRP and pantoprazole use do not show significant correlation with baseline and platelet inhibition rate.

CONCLUSIONSClopidogrel responses could be reliably detected by VerifyNow-P2Y12 assay. Female gender and high body weight are independent risk factors for clopidogrel non-responses.