Department of Clinical Laboratory, Peking Union Medical College Hospital, China

We established a new indicator of estimating erythropoietic activity, reticulocyte maturity index (RMI) using flow cytometry (FCM). A precise and sensitive parameter would be provided to monitor anemia and bone marrow transplantation.

We stained reticulocyte with fluorescent dye thiazole orange which binds to RNA. RMI was determined by the relative proportion of the highly fluorescent reticulocyte fraction to the total population (HFR%). The definition of the HFR% was based on the 95% interval of the mean fluorescence intensity of reticulocytes through testing 139 hematological normal (non-anemic) healthy adults by Coulter EPICS Elite ESP FCM. 'The reference normal range of HFR% was 0.23 - 0.47. Then we observed 4 cases peripheral blood stem cell transplantation (PBSCT) and 247 various anemia to evaluated the clinical application of the RMI.

High HFR% with increased Ret% was consistently observed on 18 patients with enhanced erythropoiesis (9 acquired auto-immune hemolytic anemia and 9 acute blood loss) and 13 patients with special dyserythropoiesis (PNH). Significantly high mean value of HFR% with a normal or reduced Ret% was shown in 42 patients at ineffective erythropoietic conditions (22 acute myeloid leukemia, 5 chronic myeloid leukemia, 7 myelo-dysplastic syndrome, 5 aplastic anemia and 3 megalobastic anemia). HFR% was still in the normal range for the patients with reduced erythropoiesis (29 chronic renal failure and 40 iron deficiency anemia). HFR% and Ret% from 60 unknown anemia patients or difference phases anemia patients treated by medicine showed a wide range. As to 45 patients with malignant hematological diseases, RMI and Ret% fell into an extreme nadir during polychemotherapy. RMI began to rise first and got beyond the normal range, meanwhile Ret% was still in low level during earlier borrow recovery. According to the detection of hematopoietic engraftment of 4 cases PBSCT, the median time of HFR% getting to 0.23 - 0.47 was 10 days, which was almost identical to the time of absolute neutrophils counts reaching to 0.2 - 0.5 x 109/l.

RMI was clinical useful in qualitatively estimating the change in erythropoiesis and provide an aid at the diagnosis of different hematological disorders. It was also a sensitive indicator at the beginning of granulocytes recovery after aplasiogenic cytostatic drug therapy to malignant hematological diseases and an early indicator to hematopoietic regeneration after PBSCT or bone marrow transplantation.

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