Comparison of Platelet Function Tests in Predicting Clinical Outcome in Patients Undergoing Coronary Stent Implantation

Context High on-treatment platelet reactivity is associated with atherothrombotic events following coronary stent implantation. Objective To evaluate the capability of multiple platelet function tests to predict clinical outcome. Design, Setting, and Patients Prospective, observational, single-center cohort study of 1069 consecutive patients taking clopidogrel undergoing elective coronary stent implantation between December 2005 and December 2007. On-treatment platelet reactivity was measured in parallel by light transmittance aggregometry, VerifyNow P2Y12 and Plateletworks assays, and the IMPACT-R and the platelet function analysis system (PFA-100) (with the Dade PFA collagen/adenosine diphosphate [ADP] cartridge and Innovance PFA P2Y). Cut-off values for high on-treatment platelet reactivity were established by receiver operating characteristic curve analysis. Main Outcome Measurement The primary end point was defined as a composite of all-cause death, nonfatal acute myocardial infarction, stent thrombosis, and ischemic stroke. The primary safety end point included TIMI (Thrombolysis In Myocardial Infarction) criteria major and minor bleeding. Results At 1-year follow-up, the primary end point occurred more frequently in patients with high on-treatment platelet reactivity when assessed by light transmittance aggregometry (11.7%; 95% confidence interval [CI], 8.9%-15.0% vs 6.0%; 95% CI, 4.2%-8.2%; P<.001), VerifyNow (13.3%; 95% CI, 10.2%-17.0% vs 5.7%; 95% CI, 4.1%-7.8%; P<.001) and Plateletworks (12.6%; 95% CI, 8.8%-17.2% vs 6.1%; 95% CI, 3.8%-9.2%; P=.005), which also had modest ability to discriminate between patients having and not having a primary event: light transmittance aggregometry (area under the curve [AUC], 0.63; 95% CI, 0.58-0.68), VerifyNow (AUC, 0.62; 95% CI, 0.57-0.67), and Plateletworks (AUC, 0.61; 95% CI, 0.53-0.69). The IMPACT-R, Dade PFA collagen/ADP, and Innovance PFA P2Y were unable to discriminate between patients with and without primary end point at 1-year follow-up (all AUCs included 0.50 in the CI). None of the tests identified patients at risk for bleeding. Conclusions Of the platelet function tests assessed, only light transmittance aggregometry, VerifyNow, and Plateletworks were significantly associated with the primary end point. However, the predictive accuracy of these tests was only modest. None of the tests provided accurate prognostic information to identify low-risk patients at higher risk of bleeding following stent implantation.