Background: Variability in response to thienopyridines has led to the development of point-of-care devices to assess adenosine diphosphate (ADP)-induced platelet aggregation. These tests need to be evaluated in comparison to reference measurements of P2Y(12) function during different thienopyridine treatments.
Methods: After a run-in on 75 mg aspirin, 110 subjects were randomized to double-blind treatment with clopidogrel 600 mg loading dose (LD)/75 mg maintenance dose (MD) or prasugrel 60 mg LD/10 mg MD. Antiplatelet effects were evaluated by VerifyNow P2Y12 (VN-P2Y12) device (Accumetrics, San Diego, CA), vasodilator-stimulated phosphoprotein (VASP) phosphorylation assay, and light transmission aggregometry (LTA). Prasugrel's and clopidogrel's active metabolite concentration were also determined.
Results: Dose- and time-dependent inhibition of P2Y(12) was evident with VN-P2Y12. There was strong correlation with VN-P2Y12 and VASP or LTA for all treatments through a wide range of P2Y(12) function. At high levels of P2Y(12) inhibition, platelet function measured by VN-P2Y12 was maximally inhibited and could not reflect further changes seen with VASP or LTA methods. Correlation was also observed between exposure to clopidogrel's active metabolite and VN-P2Y12 during MD and LD, whereas it was observed only with prasugrel MD.
Conclusion: The VN-P2Y12 correlated strongly with inhibition of P2Y(12) function, as measured with either VASP or LTA. VN-P2Y12 also correlated to exposure to the active metabolite of prasugrel and clopidogrel up to levels associated with assumed saturation of the P2Y(12) receptor.