The Diagnostic Utility of the Point-of-Care CYP2C19 Genotyping Assay in Patients with Acute Coronary Syndrome Dosing Clopidogrel: Comparison with Platelet Function Test and SNP Genotyping.

Background: Clopidogrel is a widely used antiplatelet agent for dual antiplatelet therapy and metabolized by CYP2C19. The polymorphism of CYP2C19 is associated with the therapeutic effect of clopidogrel.

Methods: A total of 119 patients diagnosed with acute coronary syndrome (ACS) and underwent percutaneous coronary intervention (PCI) with drug-eluting stents was enrolled. Polymorphisms of CYP2C19 *2,*3,*17 were determined by the Spartan RX CYP2C19 and confirmed by SNP genotyping assay. Genotype was grouped as ultra-rapid metabolizer, extensive metabolizer, intermediate metabolizer, and poor metabolizer. The degree of platelet inhibition was assessed by the VerifyNow P2Y12 system (Accumetrics, USA).

Results: The CYP2C19 genotypes were distributed as 4 (3.3%) for UM, 39 (32.8%) for EM, 54 (45.4%) for IM, 22 (18.5%) for PM by evaluation with Spartan RX CYP2C19. The numbers of patients with the *1/*17, *1/*1, *1/*2, *1/*3, *3/*17, *2/*2, *2/*3, and *3/*3 genotype were 4 (3.3%), 39 (32.8%), 40 (33.6%), 13 (10.9%), 1 (0.9%), 11 (9.2%), 10 (8.4%), 1 (0.9%), respectively. The genotyping results between Spartan RX CYP2C19 and SNP genotyping assay showed discrepancy in 2 patients. The discrepancy appeared in *17 allele analysis in both patients as false-positive result.

Conclusions: The false-positive *17 allele couldn't affect IM or PM group associated with thrombotic events, but it could affect UM group associated with bleeding events, which is relatively less investigated. Although the supplement of *17 allele detection should be accomplished, this novel point-of-care CYP2C19 genotyping instrument could determine the response to the clopidogrel and support the appropriate treatment of ACS patients.