Reticulated platelet counts in patients undergoing autologous bone marrow transplantation: an aid in assessing marrow recovery.

Thiazole orange (TO) is a fluorescent dye that is commonly used for flow cytometric measurement of erythrocytic reticulocytes. This technique has also been validated for counting "reticulated" platelets, as a measure of bone marrow thrombopoietic activity. Patients with an established diagnosis of idiopathic thrombocytopenic purpura (ITP) have been reported to have a three- to five-fold increase in the percent of circulating reticulated platelets. The current study was conducted to determine if platelet reticulocyte counts predicted recovery of bone marrow thrombopoietic activity following autologous bone marrow transplantation. We found an increase in the percent of circulating reticulated platelets preceding recovery of the platelet count; then, as the patients' platelet counts rose, the percent reticulated platelets fell. In patients with prolonged thrombocytopenia, a persistent increase in the proportion of reticulated platelets suggested a consumptive process, as opposed to failure of engraftment. Moderate transfusion of platelet concentrates did not interfere with the ability of the platelet reticulocyte measurements to detect increased thrombopoietic activity. Platelet transfusions did obscure any decrease in the proportion of reticulated platelets. Our results show that platelet reticulocyte counts could be useful in monitoring the recovery of marrow function following autologous bone marrow transplantation.