The standardized normal Ivy bleeding time and its prolongation by aspirin.

W HEN VESSELS ARE CUT OR INJURED, platelets adhere to exposed collagen and then to each other to form aggregates called primary hemostatic plugs. These plugs stop bleeding from the small skin vessels that are cut in performing a bleeding time. Therefore, the bleeding time is a test of the ability of platelets to function normally in the first step of hemostasis. The clinical usefulness of the bleeding time has been limited by difficulties in standardizing the test. As originally described by Duke,’ vessels in the ear lobe were incised. Ivy and co-workers2’3 increased the sensitivity of the test by puncturing the skin of the forearm while applying a back pressure of 40 mm. of mercury to the cut vessels. Borchgrevink and %Valler modified the Ivy technic by substituting blade incisions for puncture wounds. Using this technic, we have occasionally obtained different bleeding times from successive incisions in the same patient because of difficulty in reproducing the depth of incisions. Some years ago, Frick5 described abnormal bleeding after aspirin in 3 patients whose hemostatic abnormalities were corrected when the aspirin was stopped. Quick recently reported6 that prolongation of the bleeding time after aspirin could be used to detect patients with von Willebrand’s disease who had a normal or only slightly prolonged bleeding time before aspirin. This report prompted us to study further the effect of aspirin upon the bleeding time in various hemorrhagic disorders. The first step in this study, reported