Effect of bodyweight on VerifyNow Aspirin platelet function test: a retrospective review.

Abstract

Antiplatelet therapy is used to prevent stent thrombosis in intracranial stents, but the optimal dose of aspirin is unknown. This study sought to determine whether the degree of platelet inhibition with aspirin is affected by bodyweight as observed through a platelet reactivity assay. This is a retrospective review of patients who underwent neurovascular stent placement and had a VerifyNow Aspirin assay result. The primary outcome was the correlation between the VerifyNow Aspirin result, bodyweight, and the initial dose of aspirin. Secondary outcomes included the impact of the VerifyNow P2Y12 result and of weight on the incidence of bleeding or a thrombotic event. Of the 142 included patients, 62.7% weighed ≥70 kg and 88.7% were initiated on aspirin 300-325 mg daily. 83.8% achieved a therapeutic VerifyNow Aspirin result. There was minimal correlation between the VerifyNow Aspirin result, bodyweight, and aspirin dose (R²=0.02). Between patients who weighed <70 kg versus ≥70 kg, there was no difference in the mean aspirin reaction units (ARU) (449 vs 435, p=0.32) or in the incidence of bleeding (28% vs 17.1%, p=0.14) or a thrombotic event (4% vs 5.3%, p=0.59). No patient experienced stent thrombosis and eight patients experienced in-stent stenosis. In a multivariate analysis, only the VerifyNow P2Y12 result predicted the development of either bleeding or a thrombotic event (p<0.01). Bodyweight did not influence the likelihood of obtaining a therapeutic VerifyNow Aspirin result. The clinical utility of obtaining VerifyNow Aspirin assays for this patient population is unknown.