Monitoring platelet inhibition after clopidogrel with the VerifyNow-P2Y1® rapid analyzer:: The VERIfy Thrombosis risk ASsessment (VERITAS) study

Introduction: Clopidogrel inhibits platelet P2Y12 ADP receptors, while ADP, as an inductor of aggregation, stimulates both P2Y12 and P2Y1 platelet receptors. Despite a clinical loading dose routine with clopidogrel, some patients still experience study coronary stent thrombosis suggesting persistent platelet activation. The VerifyNow-P2Y12 is a rapid assay that test platelet activity over 3 min and uses of the combination of ADP and prostaglandin E1 (PGE1) to directly measure the effects of clopidogrel. on the P2Y1 2 receptor. ADP is used to maximally activate the platelets by binding to the P2Y1 and P2Y12 platelet receptors, while PGE1 is used to suppress the ADP-induced P2Y1-mediated increase in intracellular calcium levels. Objective: The VERIfy Thrombosis risk ASsessment (VERITAS) was a prospective study designed to measure platelet response to clopidogrel therapy in subjects with multiple risk factors or history of vascular disease using this novel point-of-care assay. Methods: 166 participants were enrolled in 4 participating sites. Data from 147 participants were analyzed after exclusion of 19 patients due to protocol violations. Platelets were assessed twice at baseline (before clopidogrel) and at 24 h post-loading 450mg (110 participants) or 7 days after chronic clopidogrel treatment (75 mg/day) (37 patients). All participants received aspirin 81-325 mg for at least 2 days before the study enrollment. Results from the VerifyNow-P2Y12 assay are reported in P2Y12 reaction units (PRU). Results: Clopidogrel therapy resulted in a mean 64.0 +/- 25.3% PRU reduction. No participant reached PRU inhibition below 10% of baseline. Distribution of PRU values for the VerifyNow-P2Y12 assay shows a separation from baseline to post-clopidogrel assay values with some overlap due to high inter-individual variations in response. Conclusions: VerifyNow-P2Y12 is a reliable, fast and sensitive device suitable for monitoring of platelet inhibition during clopidogrel therapy. (c) 2006 Elsevier Ltd. All rights reserved.