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  • Title: Platelet reactivity and clopidogrel resistance are associated with the H2 haplotype of the P2Y12-ADP receptor gene.
    Author: Staritz P, Kurz K, Stoll M, Giannitsis E, Katus HA, Ivandic BT.
    Journal: Int J Cardiol; 2009 Apr 17; 133(3):341-5. PubMed ID: 18485500.
    Abstract:
    BACKGROUND: Platelet hyperreactivity was reported in clopidogrel-naiotave carriers of the H2 haplotype of the P2Y(12) platelet ADP receptor. Here, we studied the influence of this genetic variant on clopidogrel responsiveness. METHODS: ADP-mediated (5 micromol/L) platelet aggregation was determined by impedance (Omega) aggregometry in 43 clopidogrel-naïve blood donors and 557 patients treated with aspirin and clopidogrel after percutaneous coronary stent implantation. A cut-off of 5 Omega was used to classify the aggregation response. Haplotype tagging single nucleotide polymorphism G52T was genotyped using a TaqMan assay. RESULTS: The number of H2 alleles correlated with aggregation in clopidogrel-naïve subjects in healthy subjects (p=0.041): impedance results were 8.4+/-3.6, 10.5+/-1.6 and 12.5+/-2.1 Omega in carriers of the H1/H1 (n=30), H1/H2 (n=11) and H2/H2 (n=2) haplotypes, respectively. 87.1% (n=485) and 12.9% (n=72) of clopidogrel treated patients were responders and nonresponders, respectively. Women were more likely to be nonresponders (O.R. 3.90 [95% CI 2.34-6.50]). Carriers of a H2/H2 haplotype (n=14) exhibited stronger aggregation than patients with at least one H1 allele (6.3+/-7.5 vs. 1.8+/-3.3 Omega, p=0.0212) and were more frequently nonresponders (p=0.004). Consequently, the H2/H2 haplotype was associated with clopidogrel resistance (O.R. 5.42 [95% CI 1.82-16.11]). This risk factor was independent of the gender effect. CONCLUSIONS: This is the first large study in clopidogrel treated patients suggesting that a homozygote H2 genotype contributes to clopidogrel resistance. The clinical significance of this finding remains to be demonstrated.
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