Antiplatelet Drug Response Status Does Not Predict Recurrent Ischemic Events in Stable Cardiovascular Patients

BACKGROUND: The biological response to antiplatelet drugs has repeatedly been shown to predict the recurrence of major adverse cardiovascular events (MACEs). However, most studies involved coronary artery disease patients with recent vessel injury shortly after the initiation of antiplatelet therapy. Data on stable cardiovascular patients are scarce, and the added predictive value of specific assays (the vasodilator phosphoprotein assay for the clopidogrel response and serum thromboxane B2 for the aspirin response) and aggregation-based assays relative to common predictors has rarely been addressed. METHODS AND RESULTS: Stable cardiovascular outpatients participating in the Antiplatelet Drug Resistances and Ischemic Events (ADRIE) study (n=771) were tested twice, at 2 separate visits, with specific and aggregation-based assays. Follow-up lasted 3 years, and <1% of patients were lost to follow-up. MACEs were adjudicated by an independent committee. Multivariate survival analyses included relevant variables identified in univariate analysis and platelet function test results. The C-index was used to express the prognostic value of various multivariate models. MACEs, the primary end point, occurred in 16% of patients. Hypertension, smoking, older age, and elevated low-density lipoprotein cholesterol were predictive of MACE recurrence, with a C-index of 0.63 (P<0.001). Neither the specific nor the aggregation-based assays added significant predictive value for the primary end point. CONCLUSIONS: Biological antiplatelet drug responsiveness, measured with specific or aggregation-based assays, has no incremental predictive value over common cardiovascular risk factors for MACE recurrence in stable cardiovascular outpatients. These results do not support platelet function testing for MACE risk evaluation in stable cardiovascular patients. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00501423.