Fig. (3) Time-dependent increase of ADP-induced platelet aggregation after venipuncture. Means ± SEM of maximal value in ohms after application of 5 µM ADP to whole blood. Half-time of the fitted curve was 8.8 minutes. Blood was collected from subjects (n=8) who had not ingested a COX-2 inhibitor, and was kept in closed tubes at room temperature.