Residual platelet reactivity to predict long-term clinical outcomes after clopidogrel loading in patients with acute coronary syndromes: comparison of different cutoff values by light transmission aggregometry from the responsiveness to clopidogrel and stent thrombosis 2-acute coronary syndrome (RECLOSE 2-ACS) study

The aim of this study was the identification of the optimal cutoff value of high residual platelet reactivity (HRPR) assessed by light transmission aggregometry (LTA) in the responsiveness to clopidogrel and stent thrombosis 2-acute coronary syndrome (RECLOSE 2-ACS) patient cohort to discriminate patients with and without major adverse cardiac events (MACE) and cardiac death at 2 years. The RECLOSE 2-ACS study included 1,789 patients with ACS who underwent LTA after clopidogrel loading. A post hoc cutoff value for HRPR was defined with the ROC curve and the Youden index and compared with the protocol-defined cutoff of 70 %. By ROC analysis, 63 % resulted the optimal cutoff value to predict both MACE and cardiac death at 2 years follow-up. A significant sensitivity improvement for the ROC-based cutoff value was noted (p < 0.001), at the price of lower specificity and predictive accuracy. The latter were 81 % for MACE and 85 % for cardiac death with the 70 % cutoff, while the respective figures were 73 and 75 % with the 63 % cutoff. The areas under the curve were virtually identical with the 70 and 63 % cutoffs both for MACE (0.71) and cardiac death (0.79). A residual platelet reactivity cutoff of 70 % by LTA, compared to the ROC-based cutoff of 63 %, allows for the identification of a subset of patients at very high risk of adverse ischemic events, making LTA-ADP test more acceptable in clinical practice for the identification of subjects at risk than other platelet function assays with broader definitions of HRPR.