In vitro bleeding test--a simple method for the detection of aspirin effects on platelet function.

We investigated platelet function of 21 healthy blood donors before, 4 hrs and 1 to 7 days after a single oral dose of 0.02 (n = 3), 0.05 (n = 3), 0.1 (n = 3), 0.5 (n = 2) and 1.0 g (n = 10) aspirin. Three additional donors received 0.02 g aspirin/day for 5 days. A new and simple in vitro bleeding test (Thrombostat) using whole blood was far more sensitive than all other tests for platelet function (subaquatic bleeding time, thrombelastrogram, resonance-thrombogram, platelet adherence, spreading and aggregation). With this method using 2mM CaCl2 as additional agent all donors showed significantly increased in vitro bleeding volumes, for at least 2 days after ingestion of 0.1 to 1 g aspirin. In the majority of cases the aspirin effect could be detected even after 5-6 days. In 2 of 3 donors even 0.05 g aspirin was detectable. There was already a definite effect seen after 2 days in all 3 cases when 0.02 g was ingested daily. The new in vitro bleeding test should be suitable for the control of low dose aspirin prophylaxis of arterial thromboembolic disorders.