Abstract 2983: Prevalence of Aspirin Resistance and Association Factors in Patients with Ischemic Stroke Using the Rapid Platelet Function Assay
Background: Ischemic stroke may recur in many patients with previous ischemic events despite of taking antiplatelet drugs for secondary prevention. However, the proper laboratory test for monitoring antiplatelet therapy is not available in clinical situation. The rapid platelet function assay (VerifyNow™ Aspirin) has been recently developed and used.
Objectives: The purposes of this study were to determine the frequency of aspirin resistance in patients with ischemic stroke and to identify the factors related with aspirin resistance using the rapid platelet function assay.
Methods: We consecutively enrolled 136 stroke patients taking aspirin regularly for secondary prevention. We used the VerifyNow™ Aspirin to measure the inhibition of platelet function by aspirin. An aspirin reaction unit (ARU) values ≥ 550 indicates the absence of aspirin-induced platelet dysfunction. Demographic data, vascular risk factors (hypertension, diabetes, hyperlipidemia, obesity: BMI ≥ 25), the presence of metabolic syndrome (defined as ATP-III guideline), drug history, hemoglobin and platelet counts were recorded.
Results: Twenty-four (17.6%) patients were identified as aspirin non-responders (defined as ARU ≥ 550) on the platelet function test. Metabolic syndrome was more often found in aspirin non-responders than in aspirin responders (66.7% vs. 41.9%, p = 0.04). There was no significant difference between aspirin responders and aspirin non-responders concerning age, gender, hypertension, diabetes mellitus, hyperlipidemia, obesity, hemoglobin, and platelet counts. The aspirin formula, dose and duration of treatment were not significantly different between the two groups. Three (50%) of six patients who had taken aspirin medication prior to ischemic events showed insufficient platelet inhibition on the blood test.
Conclusions: Aspirin resistance in ischemic stroke patients is not uncommon. Metabolic syndrome may be associated with the aspirin resistance on the platelet function assay. The further studies will be required to determine the prognostic value of the rapid platelet function test.