Prolonged bleeding time with adequate platelet count in hospital patients.

100 patients with a modified Ivy bleeding time longer than 10 min in the presence of more than 80 x 10(9)/l blood platelets were studied retrospectively. 72 patients had repeated bleeding times between 10 and 20 min or one or more measurements exceeding 20 min, and were considered to have an unquestionable platelet dysfunction. 39 (54%) of these 72 patients were receiving large doses of antibiotics. Nearly one half of the patients on antibiotics had a bleeding tendency, but most of these patients had additional features that may have interfered with platelet function, or a coagulation defect. In the remaining 33 patients, the prolonged bleeding time was associated with von Willebrand's disease, liver disease, leukaemia/myeloproliferative disease, paraproteinaemia or aspirin ingestion. High doses of penicillin seem to be the most common cause of qualitative platelet disorders in general hospital practice.