Correlation between the results obtained by flow cytometric evaluation of platelet activation parameters and VerifyNow-P2Y
test in patients receiving antiplatelet therapy. The percent of inhibition (% inhibition) was plotted against the percentage of platelets that expressed P-selectin (CD62P) after stimulation with 20 μM ADP and 5 μg/mL collagen type I for 110 min at room temperature in the presence of 1 μM PG E1. (§) First quartile of control values for CD62P expression. Patients receiving antiplatelet therapy with levels of CD62P expression and PAC-1 binding above this limit were defined as "Low-responder"; those with both values below this limit were defined as "High-Responder"; those with one value above and the other below the corresponding limit were defined as "Intermediate-responder". ($) Cut-off value for % of inhibition in the VerifyNow-P2Y12 test giving minimal false negative and positive results (see Figure 1).