Abstract
We measured the percentage of circulating platelets that were stained supravitally for RNA with thiazole orange (TO), a fluorescent dye, in patients with various thrombocytopenic disorders. In patients with acute idiopathic thrombocytopenic purpura, the percentage values of TO-positive platelets were significantly elevated over those in normal control. However, the percentage values of TO-positive platelets in patients with aplastic anemia remained within the range of normal control. These findings suggest that the elevated percentage of TO-positive platelets reflects the activation of thrombopoiesis in the bone marrow. An apparent elevated percentage of TO-positive platelets was noticed at the recovery phase from chemotherapy-induced thrombocytopenic nadir in patients with leukemia and malignant tumor. Thus we confirmed that TO-positive platelet was one marker of thrombopoietic activity. Serial measurements of TO-positive platelets during recovery from cytopenic nadir with stem cell transplantation, by using a granulocyte colony-stimulating factor, showed that the neutrophile progressively returned to increase before the percentage of TO-positive platelets and reticulocytes elevated. These observations indicate that TO analysis is potentially a reliable method of estimating platelet production.
