The stratification of platelet reactivity and activation in patients with stable coronary artery disease on aspirin therapy

Condensed abstract: Heightened platelet reactivity may affect the occurrence of ischemic events in patients with coronary artery disease on aspirin therapy. However, a definition to stratify platelet reactivity in this group of patients has not been previously reported. We studied platelet reactivity and activation by measuring platelet aggregation and the expression of p-selectin, total GP IIb/IIIa and active GP IIb/IIIa (n=96). Patients were divided into quartiles by each of the markers; correlations were made between the markers; and a definition of heightened platelet reactivity was proposed. Marked variability in activation and reactivity were observed despite aspirin therapy. Background: Heightened platelet reactivity and activation may affect the occurrence of ischemic events in patients with coronary artery disease on aspirin therapy. However, a definition to stratify platelet reactivity has not been previously reported. Methods and results: Platelet aggregation (5 and 20 μmol/l ADP), total GP IIb/IIIa, active GP IIb/IIIa and the expression of maximally stimulated p-selectin were measured in patients about to undergo elective coronary stenting (n=96). All patients had received aspirin (325 mg). There was marked variability in platelet reactivity and activation as measured by all markers. The highest quartile was defined by 77±1% and 98±1% aggregation by 5 and 20 μmol/l ADP, respectively; 65±2% p-selectin positivity; 508±15 MFI for total GP IIb/IIIa; and 23.0±1.8 MFI for active GP IIb/IIIa. Conclusions: There is a wide range in platelet reactivity and activation as measured by multiple markers in stable coronary disease patients on aspirin therapy. From these indices, we can define those patients at the extremes of reactivity and activation and thus, the greatest potential risk of thrombosis and bleeding. These indices will serve as a guide to future studies investigating the relationships of platelet reactivity, activation, drug-induced inhibition and clinical outcomes.