Effect of increasing doses of aspirin on platelet function as measured by PFA-100 in patients with diabetes

INTRODUCTION: Platelets of diabetic patients have been reported to be less sensitive to aspirin. The aim of this study is to compare a medium (300 mg) and low (100 mg) dose of aspirin on platelet function in diabetic patients. METHODS: We have included one hundred and two patients with type 2 diabetes mellitus. Platelet function was measured as closure time (CT) with the Platelet Function Analyzer (PFA)-100 before the administration of aspirin. Initially the patients were given 100 mg aspirin once daily for seven days, and then the measurements were repeated. If the CT exceeded the upper limit of 300 s, the study was terminated. If not, the patients continued the aspirin therapy with a dose of 300 mg daily for another seven days, and the CTs were measured again. RESULTS: After taking 100 mg aspirin, the CT significantly increased from 126+/-29 s to 256+/-66 s (p<0.001). In 68 of 102 (67%) patients, the CT increased to 300 s. In the remaining 34 patients, the baseline CT was 113+/-29, and increased to 170+/-45 s after 100 mg aspirin (p<0.001). In these patients, there was a further increase in the CT from 170+/-45 to 229+/-75 s following 300 mg aspirin (p<0.001). On average, the CT was increased by 60% and 39% following ingestion of 100 and 300 mg aspirin, respectively. CT>300 s were obtained in 15 (44%) of 34 patients after 300 mg aspirin. CONCLUSIONS: Although, a daily dose of 100 mg aspirin effectively inhibited platelet function in a majority of diabetics, a considerable proportion of patients showed a greater platelet inhibition with the use of 300 mg aspirin. The PFA-100 closure time may be used to separate those patients who require a higher dose of aspirin to achieve desired antiplatelet effect.