Thresholds for platelet reactivity to predict clinical events after coronary intervention are different in patients with and without diabetes mellitus

Patients with diabetes mellitus (DM) have increased baseline platelet reactivity and impaired response to antiplatelet drugs, compared to non-diabetics. Aim of the present study was to investigate whether thresholds for high platelet reactivity (HPR) that predict clinical outcomes after percutaneous coronary intervention (PCI) are similar in diabetic compared to non-diabetic patients. A total of 640 (32.6% with DM) consecutive patients taking aspirin and clopidogrel undergoing elective PCI were recruited. Platelet reactivity was measured immediately before the procedure with the VerifyNow P2Y12 assay. Primary end point was the 30-day incidence of major adverse cardiac events (MACE) in relation to the presence of DM and to P2Y12 reaction units (PRU) distribution. The optimal cut-off to predict 30-day MACE was a PRU value of >256 in diabetics, and a PRU value of >229 in non-diabetics. Accordingly, we redefined HPR on the basis of these two specific thresholds (HPR-ST), now including 60/209 (29%) diabetic patients with PRU >256, and 130/431 (30%) non-diabetic patients with PRU >229. HPR-ST discriminates significantly (p < 0.001) patients with and without MACE, with a diagnostic accuracy of 73%. The combination of DM and HPR-ST resulted in the highest incidence of MACE (23.3%; p for trend <0.001). At multivariate analysis, HPR-ST was the strongest independent predictor of 30-day MACE (odds ratio 4.80, 95% confidence interval 2.58-8.93; p < 0.001). Redefining HPR based on specific thresholds for patients with and without DM significantly improves prediction of MACE post-PCI. Patients with HPR-ST, especially in the presence of DM, are at increased risk for ischemic events and may benefit from more aggressive antiplatelet strategies.