Chronic kidney disease--is it a true risk factor of reduced clopidogrel efficacy in elderly patients with stable coronary artery disease?

Background: Chronic kidney disease (CKD) is an established predictor of recurrent ischemic events in patients with coronary artery disease (CAD). This association has been partially ascribed to high post-treatment platelet reactivity (HPPR) according to platelet function testing. However, the influencing factors of HPPR are assay-dependent, and the relevant data of elderly patients with stable CAD are absent.

Patients And Methods: 310 elderly patients (>80years of age) with stable CAD taking prolonged maintenance clopidogrel (75mg/day) were studied. Maximal platelet aggregation rate (MPA%) with light transmittance aggregometry and Platelet Reactive Units (PRU) with VerifyNow (VN) P2Y12 system were obtained. Markers of platelet activation, including PAC-1 and CD62P, were also determined.

Results: Patients on different stages of CKD presented similar MPA% and expression of PAC-1 and CD62P. Although severe CKD patients were more likely to present HPPR identified by VNP2Y12 (odds ratio: 1.85, p=0.038), multiple logistic regression diminished this effect (adjusted odds ratio: 1.19, p=0.642), and revealed anemia as a possible predictor of HPPR (adjusted odds ratio: 5.92, p=0.001). However, in a parallel way, hemoglobin correlated with baseline PRU values as well as with post-treatment values (r=-0.624 and r=-0.463, respectively, p<0.001). Association between hemoglobin and PRU inhibition rate was not found. Moreover, hemoglobin exerted no influence on MPA% at all.

Conclusion: CKD is not necessarily associated with reduced antiplatelet effects of clopidogrel in elderly patients with stable CAD taking prolonged maintenance clopidogrel, and the seemingly influence of CKD on HPPR assessed by VNP2Y12 assay may be due to the artifactual effect of hemoglobin on VNP2Y12.