Platelet function testing offers the possibility to individualize antiplatelet therapy in coronary artery disease patients but failed to improve clinical outcomes in randomized trials. However, high-on-treatment platelet reactivity (HPR) remains a risk factor for recurrent ischemic events and low-on-treatment platelet reactivity (LPR) is a risk factor for bleedings.

We collected data of patients assigned to the monitoring arm of the randomized ARCTIC and ANTARCTIC trials that evaluated the platelet reactivity by the VerifyNow P2Y12 test two weeks after coronary stenting. HPR was defined by PRU≥208, LPR by PRU≤85 and optimal platelet reactivity (OPR) by 85.

Among the 1418 patients included, HPR was present in 269 patients (18.9%), OPR was reached in 681 patients (48.0%) and LPR in 468 patients (33.0%). The primary composite endpoint occurred in 9.7%, 11.5% and 14.3% respectively. There was no significant difference in the net clinical benefit between HPR and OPR patients (adjusted HR: 0.91(0.48–1.72); P=0.77) and between LPR and OPR patients (adjusted HR: 1.13 (0.67–1.90); P=0.64). There were no difference in the individual clinical endpoints between the three groups. ROC curve analysis demonstrated that PRU when used for treatment adjustment has a limited ability to discriminate net clinical benefit, ischemic or bleeding complications (curve–c index=0.55, 0.51 or 0.59, respectively).

Two weeks after stenting, an optimal platelet reactivity was obtained in less than half of the population. The net clinical benefit of these patients was not different from that of patients with HPR and LPR who had treatment adjustment.