Implication of aspirin resistance: Simple laboratory finding or important clinical criteria? / 대한내과학회지

Aspirin resistance defined by light transmittance aggregometry (LTA) or urinary 11-dehydro-thromboxane B2 has been associated with an increased risk of adverse clinical events. However, aspirin resistance based on the point-of-care VerifyNow-Aspirin assay (aspirin reaction unit > or = 550) shows poor sensitivity compared with LTA. In aspirin-treated patients, activation by cyclooxygenase- independent pathways may be associated with residual platelet reactivity, which may cause adverse clinical outcomes in some portion. A large-scale, prospective study using several platelet function assays should be performed to establish the long-term clinical significance of antiplatelet resistance in Korean patients treated with coronary stenting. Accordingly, we can apply tailored antiplatelet therapy in resistant patients.

Incidence of Aspirin Resistance in the Patient Group of a University Hospital in Korea / 대한진단검사의학회지

BACKGROUND: Aspirin is the most common drug used for the prevention of arterial thrombosis. However, platelet responsiveness to aspirin is variable among individuals and it is important to detect aspirin resistance to improve clinical outcome. We analyzed the changes of platelet reactivity before and after aspirin treatment. We also investigated the incidence and influencing factors of aspirin resistance in Korean. METHODS: We tested platelet function in 198 patients who had been treated with aspirin in a Korean university hospital, and 59 of these patients were tested for platelet function before and after aspirin treatment. We also analyzed platelet reactivity in 136 patients who had not been treated with aspirin. Platelet function was tested using the VerifyNow Aspirin Assay (Accumetrics, USA). Platelet reactivity was expressed as aspirin reaction unit (ARU) and > or =550 ARU was defined as aspirin resistance. RESULTS: Platelet reactivity of 136 patients who had not been treated with aspirin was 632.2+/-46.3 ARU (mean+/-SD) (range, 462-675). Platelet reactivity of 198 patients who had been treated with aspirin was 472.5+/-60.0 (338-666) ARU, and 10.1% of patients were aspirin-resistant. The difference of platelet reactivity before and after aspirin treatment was 128.3+/-68.7 (-40-248) ARU. Hb level was lower and platelet count was higher in aspirin-resistant group than in aspirin-sensitive group (P<0.05). CONCLUSIONS: We demonstrated the distribution of platelet reactivity before and after aspirin treatment using the VerifyNow Aspirin Assay. The incidence of aspirin resistance was 10.1%, and low Hb level and high platelet count were related with aspirin resistance.