Usefulness of the VerifyNow P2Y12 assay to evaluate the antiplatelet effects of ticagrelor and clopidogrel therapies

Objectives We analyzed the antiplatelet effects of different P2Y(12) receptor blockers with VerifyNow P2Y12 assay (VN-P2Y12) and light transmittance aggregometry (LTA). Background The point-of-care VN-P2Y12 has been used to assess the antiplatelet effects in clopidogrel-treated patients but has not been evaluated in detail in patients treated with ticagrelor. Methods Patients were randomly assigned to either ticagrelor [180 mg loading/90 mg twice daily (n = 37)] or clopidogrel [600 mg loading/75 mg daily (n = 39)] on top of aspirin treatment, and platelet reactivity was measured serially during onset, maintenance, and offset phases. High on-treatment platelet reactivity (HPR) was defined as 5 and 20 mu M adenosine diphosphate-induced maximal platelet aggregation >= 46% and >= 59%, respectively, and P2Y12 reaction units >= 235. Results Platelet function measured by VN-P2Y12 correlated well with LTA (.812 <= rho <= .823, P < .001). VN-P2Y12 "BASE" values were consistent during administration of both agents. Calculated and reported percent inhibitions by VN-P2Y12 were similar (difference, -0.6%; 95% agreement limits, -22.9% to 21.6%). Platelet inhibition by VN-P2Y12 during clopidogrel and ticagrelor administrations was comparable to platelet inhibition by LTA. HPR determined by LTA and VN-P2Y12 were well matched, and the risk stratification between the two methods showed strong agreement after both therapies (kappa > .7). Conclusions The VerifyNow P2Y12 assay is effective in assessing the antiplatelet effects and in identifying HPR during clopidogrel or ticagrelor therapy. (Am Heart J 2012;164:35-42.)