Automated reticulocyte counting for monitoring patients on chemotherapy for acute leukaemias and malignant lymphomas.

Flow cytometric reticulocyte counting including their maturation fractions was performed with a Sysmex R-3000 automated analyser during follow-up after induction and/or consolidation with combination chemotherapy in patients with acute leukaemias (AL, n = 39; 58 courses) and malignant lymphomas (ML, n = 21; 29 courses). The ML patients received granulocyte colony stimulating factor (G-CSF) in addition after chemotherapy. During the leucopenic phase only reticulocytes of low fluorescence ratio (LFR) at extremely low concentration (< 10 x 10(9)/l) were found. After a median interval of 17 days (range 8-43), the middle fluorescence fraction (MFR) began to rise, preceding high fluorescence ratio (HFR) reticulocytes by a median of 1 day in AL patients with complete or partial remission. In ML patients, MFR and HFR reticulocytes appeared more often simultaneously after a median interval of only 11 days (range 8-15) and increased faster during the first week of marrow recovery showing a pattern different from AL. Granulocytes passed the critical limit of 0.5 x 10(9)/l at a median of 5 days after appearance of MFR reticulocytes in AL but in ML on the same day as MFR and HFR (day 0). The absolute reticulocyte concentration reached the lower limit of the reference range after about 10 days in AL. Thus, finding MFR and, to a lesser extent, HFR at very low cell concentrations, may serve as sensitive early indicators of marrow recovery after chemotherapy and are much more sensitive parameters than the absolute reticulocyte concentration. The higher median values for reticulocytes (total, HFR and MFR) after G-CSF therapy suggests that G-CSF is not lineage specific and may also stimulate erythroid precursor cells.