ABSTRACT
BACKGROUND: Aspirin resistance (AR) in platelet function assays showed substantial variation depending on the methods used to evaluate it. METHODS: In this study, we prospectively compared the results of Multiplate impedance platelet aggregometry (IPA) with those of light transmission aggregometry (LTA) and VerifyNow(R) system in determination of the prevalence of aspirin resistance (AR) and investigated the correlation between its presence and poor outcome (modified Rankin scale >2) in 105 patients with aspirin after acute ischemic stroke (AIS). RESULTS: After 5 days of using aspirin, 15 patients (14.3%) were classified as aspirin-resistance with the use of IPA, 24 patients (22.9%) by the LTA, and 14 patients (13.3%) by VerifyNow. Good agreement between the results of IPA and VerifyNow, was found (R=0.674, P<0.01). The concordance rate of AR detection was high between VerifyNow and IPA (k=0.72, P<0.01), albeit quite low between LTA and IPA. Regarding on its influence on clinical outcome after AIS, there wasn't any significant relationship between occurrence of poor outcome and the presence of AR in three platelet function assays. CONCLUSION: This study reveals that the incidence of AR in AIS might be highly test-specific. IPA seems to be similar to VerifyNow as a platelet function test.