The Bleeding Time Response to Aspirin: Identifying the Hyperresponder

The authors measured the template bleeding time in 11 normal people before and 2, 4, 12, 24, and 48 hours after the subjects ingested a single dose of 74 mg of aspirin (ASA). The entire experiment was repeated twice at two-week intervals, with the dose of ASA increased to 325 mg and finally 3,900 mg. The mean increase was maximal at 4 and 12 hours, regardless of the dose administered, with a return to baseline by 48 hours. The authors then performed bleeding times in a prospective randomized double-blinded fashion on an additional 39 subjects at baseline and seven hours after they ingested either placebo or ASA 325 mg. The mean baseline bleeding time was 5.2 minutes (SD ± 1.4), with a mean prolongation after ASA of 2.1 minutes (SD ± 1.9). The authors identified 5 of 37 (14%) subjects as hyperresponders (HRs) using the criterion of a bleeding time prolongation of greater than 5.9 minutes (greater than 2 SD beyond the mean prolongation). Neither baseline bleeding time, threshold sensitivity of collagen-induced platelet aggregation, nor other tests of hemostatic function discriminated HRs from normals. The authors conclude that in subjects with normal baseline bleeding times, a prolongation of greater than 5.9 minutes when measured seven hours after the administration of a single dose of 325 mg of ASA can discriminate HRs from normals.