Platelet function in preleukaemia.

Platelet function was studied in 17 patients with preleukaemia and the results were compared with those of 28 patients with other chronic myeloproliferative disorders. The test pattern included bleeding time (Ivy), platelet retention (Hellem II), PF-3 activity and availability after exposure to ADP and kaolin, and ADP-, epinephrine-, collagen- and ristocetin-induced aggregations. Platelet function was frequently impaired in patients with preleukemia. The defects were similar to those found in other myeloproliferative disorders. The most consistent finding was defective aggregation. Patients with thrombocytosis and/or with increased amounts of megakaryocytes in the bone marrow had fewer defects in platelet function. Retention defect was more common in patients with hypolobulated megakaryocytes, especially in those having a specific marker, the 5q- chromosome, in their bone marrow cells.