The Effect of a-Interferon on Bone Marrow Megakaryocytes and Platelet Production Rate in Essential Thrombocythemia

In 10 patients with previously untreated essential thrombocythemia (ET), by using "'In-labeled platelets and megakaryocyte morphometry, the relation between platelet production rate and bone marrow megakaryocytes was evaluated before and during a-2b-interferon (IFN) therapy. A highly significant decrease in platelet count occurred during IFN therapy; the platelet counts, at baseline and after 2 and 6 months of IFN therapy, were 1,102 f 345 x 109/L, 524 f 169 x 10s/L (P < .OOOl), and 476 f 139 x 10'IL (P < .OOOl), respectively. The decrement in platelet count was mainly a result of diminished platelet production rate, which at baseline and after 2 and 6 months of IFN therapy was 89 f 30 x 10'' plateletdd, 53 f 18 x 10" plateletdd (P = .0033), and 45 2 20 x 10'' plateletdd (P < .0001), respectively. Also, a slight shortening of platelet mean life-span (MLS) was ob-