Optical platelet aggregometry does not appear useful as a means of assessing the risk of recurrent vascular events in aspirin-treated patients Introduction Aspirin exerts its antithrombotic activity by permanently inactivating cyclooxygenase-1, which results in the blockade of prothrombotic thromboxane A 2 production in the platelets (1). Numerous clinical trials have furnished evidence of the efficacy of aspirin in reducing the risk of ischemic vascular events. A meta-analysis of 287 randomized antiplatelet trials, performed by the Antithrombotic TrialistsÕ Collaboration (2), doc- umented that antiplatelet therapy reduced the overall risk of serious vascular events in high-risk patients by 22% when compared with the con- trols. However, many patients develop recurrent ischemic events despite antiplatelet treatment. Earlier investigations have indicated that aspirin treatment does not result in adequate in vitro antiplatelet efficacy in 5–60% of patients with vascular disease (1, 3). There is much uncertainty concerning the clinical relevance of platelet func- tion testing (4). Some previous published studies have suggested that cerebro- and cardiovascular patients found by laboratory tests to be aspirin resistant are at an increased risk of major vascular events (5–7), but studies reporting the absence of such a correlation usually have not reached publication. We investigated whether the results of optical platelet aggregometry indicate the risk of recurrent ischemic events in a popu- lation of cerebro- and cardiovascular patients taking aspirin. Acta Neurol Scand 2008: 117: 250–254 DOI: 10.1111/j.1600-0404.2007.00937.x Copyright Ó 2007 The Authors Journal compilation Ó 2007 Blackwell Munksgaard ACTA NEUROLOGICA SCANDINAVICA Sztriha LK, Sas K, Seres E, Boda K, Lenti L, Csifcsak G, Kovacs N, Vecsei L. Optical platelet aggregometry does not appear useful as a means of assessing the risk of recurrent vascular events in aspirin-treated patients. Acta Neurol Scand 2008: 117: 250–254. Ó 2007 The Authors Journal compilation Ó 2007 Blackwell Munksgaard. Objectives – To investigate whether the results of optical platelet aggregometry indicate the risk of recurrent ischemic events. Materials and methods – Cerebro- and cardiovascular patients taking aspirin for at least 30 days were studied retrospectively. Ischemic vascular events occurring prior to testing and the presence of vascular risk factors were recorded. Results – 241 subjects were included. Among the 78 patients (32.4%) who displayed recurrent vascular episodes, the age (62.5 Æ 10.6 vs. 58.4 Æ 11.6, P = 0.009) and the proportion of hypertensives (80.8% vs. 68.1%, P = 0.040) were significantly higher when compared with the participants who exhibited single events. The degree of platelet aggregation did not differ significantly between the patients with and those without recurrent episodes. Logistic regression analysis identified only age (OR 1.033, 95% CI 1.008–1.058, P = 0.010), and not aggregation values, as a risk condition for recurrent vascular episodes. Conclusions – Results of optical platelet aggregometry were not indicative of the risk of recurrent vascular events. The role of conventional risk factors appeared to be more important. L. K. Sztriha 1 , K. Sas 1 , E. Seres 1 , K. Boda 2 , L. Lenti 1 , G. Csifcsak 1 , N. Kovacs 1 , L. Vecsei 1,3 Departments of 1 Neurology and 2 Medical Informatics, Albert Szent-Gyçrgyi Medical and Pharmaceutical Center, University of Szeged, Szeged, Hungary; 3 Neurology Research Group of the Hungarian Academy of Sciences and University of Szeged, Szeged, Hungary Key words: aspirin resistance; cerebrovascular diseases; neuropharmacology; strokes; transient ischemic attack; treatment; vascular risk factors Laszlo K. Sztriha, MD, Department of Neurology, Albert Szent-Gyçrgyi Medical and Pharmaceutical Center, University of Szeged, Semmelweis u. 6, H-6725 Szeged, Hungary Tel.: +36 62 545351 Fax: +36 62 545597 e-mail: sztriha@nepsy.szote.u-szeged.hu Accepted for publication August 20, 2007 250