Comparison of reticulated platelet count and mean platelet volume determination in the evaluation of bone marrow recovery after aplastic chemotherapy.

Reticulated platelet count provides an estimate of thrombopoiesis in the same way as reticulocyte count is a measure of erythropoiesis. We applied thiazole orange (TO) staining, followed by fluorescence-activated flow-cytometric analysis, to platelets in whole-blood samples from normal subjects and 18 aplastic patients after chemotherapy for haematologic malignancies. The percentage of TO-positive platelets in 30 control subjects was 5.7 +/- 2.4% (mean +/- 1 SD), determining the threshold of reticulated platelet positivity as up to 10.5% (mean + 2 SD). In the 18 patients studied, the mean percentage of TO-positive platelets was 4.3 +/- 1.89% during aplasia and 23.3 +/- 9.43% during bone marrow recovery, respectively (P < 0.05). All patients had a percentage of TO-positive platelets of up to 10.5%. In comparison, mean platelet volume during bone marrow recovery increased in 12 cases of the 18 patients studied. We conclude that flow cytometric analysis of reticulated platelets is a sensitive and specific test for evaluating thrombopoiesis recovery during aplastic chemotherapy, and platelet transfusion should be reconsidered in these patients.