PFA-100™ and flow cytometry: can they challenge aggregometry to assess antiplatelet agents, other than GPIIbIIIa blockers, in coronary angioplasty?

Introduction: Platelet response to inhibitors varies widely, leading to a higher risk of abrupt closure events in insufficiently treated-coronary heart disease patients. The aim of this study was to compare, in patients under various antiplatelet regimens, three platelet function assays: aggregometry, PFA-100™ and flow cytometry. These assays stand for available tests, as “ready-to-use” device (PFA-100™) and sophisticated assay (cytometry). We chose the setting of percutaneous coronary intervention as a standardized procedure to determine which test was appropriate to detect the effect of (1) an aspirin bolus in patients under long-term aspirin treatment, and (2) ticlopidin in case of stent implantation. Methods: Fifty patients under oral aspirin treatment were randomized to receive a bolus of 500 mg aspirin before angioplasty ( n=25). Ticlopidin was given at a 500 mg loading dose in the case of stent implantation ( n=38). Platelet function was assessed before, at 2 and 24 h after angioplasty. Results: Considering aspirin antiplatelet effect, the following was observed: (1) a lack of further inhibition after the bolus whatever assay was used and (2) a disagreement between aggregometry and PFA-100™ to classify patients as being poor or good aspirin responders (kappa were 0.11 and 0.28 between ADP 4 or 6 μM aggregation, respectively, and PFA-100™). Another finding was the good performance of flow cytometry, which evaluated GPIIbIIIa activation, and aggregometry, to detect ticlopidin the day after the loading dose. In contrast, PFA-100™ was insensitive to ticlopidin. Conclusion: Current assays are not interchangeable to monitor antiplatelet treatment in daily practice.