[Reticulated platelets--automated measurement and clinical utility]

Development of the method to determine reticulated platelets is briefly reviewed. A new rapid method to automatically count reticulated platelets is very recently established by our research group. The principle of the measurement of reticulated platelets is based on flow cytometry. The platelets are quickly stained with a RNA fluorescent dye, auramine O and fluorescent intensity (RNA content) and forward scatter (cell size) are measured in only 80 seconds with a reticulocyte counter, equipped with special software for analysis of reticulated platelets. Both of the reproducibility and the linearity were shown to be good. Normal percentage value for reticulated platelets was 0.98% +/- 0.41% and its absolute count was 2.12 +/- 0.69 x 10(9)/l. The absolute count was decreased in patients with reduced thrombopoiesis such as acute myeloblastic leukemia, aplastic anemia and was elevated in patients with essential thrombocythemia and in chronic myelocytic leukemia. The patients with chronic idiopathic thrombocytopenic purpura had a high percentage of reticulated platelets. An apparent rise was noticed in the percentage of reticulated platelets which preceded by several days a progressive increase in the platelet count at the recovery phase of thrombocytopenia in a couple of leukemic patients. These suggest that an automated measurement of reticulated platelets can be clinically useful to estimate thrombopoiesis in bone marrow.