MEA reliably detected the effects of aspirin. Notably, 500 mg aspirin caused complete inhibition of arachidonic acid-induced platelet aggregation for 2 days in all volunteers. Aggregation returned to baseline values with a wide interindividual variation in time course by day 5. No resting time for the blood sample was required for ASPItest or TRAPtest. These assays can be implemented as real POC tests. The reproducibility of the assays studied here is within the range of modern POC analyzers.