The appearance of reticulocytes with medium or high RNA content is a sensitive indicator of beginning granulocyte recovery after aplasiogenic cytostatic drug therapy in patients with AML.

Flow-cytometric reticulocyte counts including their maturation status were performed during follow-up of induction (n = 5) and consolidation (n = 7) polychemotherapy in nine patients with acute myeloid leukemia (AML) using a Sysmex R-3000 automated counter. The reticulocytes fell to an extreme nadir (< 0.01/pl)--as did leukocytes and platelets--and consisted of cells with low fluorescence ratio (LFR) only. After a median interval of 16 days, the fraction with medium fluorescence ratio (MFR) began to rise, preceding the reticulocytes with high fluorescence ratio (HFR) for a median of 1 day in all cases with partial (n = 1) or complete (n = 8) remission. At a median of 7 days after MFR and 5 days after HFR the granulocytes reached the critical limit of > or = 0.5/nl. The reticulocytes rose to the normal range after 9 and 7 days, respectively. Automated flow-cytometric reticulocyte counting including the maturation status has been shown to provide an accessible measure of erythroid activity, which may be of predictive value for granulocyte recovery after aplasiogenic polychemotherapy in AML patients.