Comparison of VerifyNow-P2Y12 test and flow cytometry for monitoring individual platelet response to clopidogrel. What is the cut-off value for identifying patients who are low responders to clopidogrel therapy?

Cosmo Godino, Loredana Mendolicchio, Filippo Figini, Azeem Latib, Andrew S.P. Sharp, John Cosgrave, Giliola Calori, Michela Cera, Alaide Chieffo, Alfredo Castelli, Attilio Maseri, Zaverio M. Ruggeri, Antonio Colombo

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45 Scopus citations

Abstract

Background: Dual anti-platelet therapy with aspirin and a thienopyridine (DAT) is used to prevent stent thrombosis after percutaneous coronary intervention (PCI). Low response to clopidogrel therapy (LR) occurs, but laboratory tests have a controversial role in the identification of this condition. Methods: We studied LR in patients with stable angina undergoing elective PCI, all on DAT for at least 7 days, by comparing: 1) Flow cytometry (FC) to measure platelet membrane expression of P-selectin (CD62P) and PAC-1 binding following double stimulation with ADP and collagen type I either in the presence of prostaglandin (PG) E1; 2) VerifyNow-P2Y12 test, in which results are reported as absolute P2Y12-Reaction-Units (PRU) or % of inhibition (% inhibition). Results: Thirty controls and 52 patients were analyzed. The median percentage of platelets exhibiting CD62P expression and PAC-1 binding by FC evaluation after stimulation in the presence of PG E1 was 25.4% (IQR: 21.4-33.1%) and 3.5% (1.7-9.4%), respectively. Only 6 patients receiving DAT (11.5%) had both values above the 1st quartile of controls, and were defined as LR. Evaluation of the same patients with the VerifyNow-P2Y12 test revealed that the area under the receiver-operating-characteristic (ROC) curve was 0.94 (95% CI: 0.84-0.98, p < 0.0001) for % inhibition and 0.85 (0.72-0.93, p < 0.005) for PRU. Cut-off values of ≤ 15% inhibition or 213 PRU gave the maximum accuracy for the detection of patients defined as having LR by FC. Conclusion: In conclusion our findings show that a cut-off value of ≤ 15% inhibition or 213 PRU in the VerifyNow-P2Y12 test may provide the best accuracy for the identification of patients with LR.

Original languageEnglish (US)
Article number4
JournalThrombosis Journal
Volume7
DOIs
StatePublished - May 6 2009
Externally publishedYes

ASJC Scopus subject areas

  • Hematology

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