FLOW CYTOMETRIC RETICULOCYTE MATURITY INDEX - A USEFUL LABORATORY PARAMETER OF ERYTHROPOIETIC ACTIVITY IN ANEMIA

Flow cytometric reticulocyte analysis is superior to manual reticulocy te counting with respect to precision and sensitivity, Furthermore, be cause the fluorescence intensity of reticulocytes is directly proporti onal to the erythrocyte RNA content, flow cytometric analysis using th iazole orange gives a quantitative reticulocyte maturity index (RMI). Previous studies have demonstrated that the RMI parameter is the earli est indicator of bone marrow engraftment following transplantation. In the present study, we analyzed the correlation of the RMI to standard red cell parameters, reticulocyte percentage, and absolute reticulocy te count in 413 anemic patients, The correlation of RMI to serum eryth ropoietin (Epo) and serum transferrin receptor (TfR) was analyzed in a subset of anemic blood samples. We found weak correlations between th e RMI and hemoglobin (r(2) = 0.041), hematocrit (r(2) = 0.038), reticu locyte percentage (r(2) = 0.078), and absolute reticulocyte count (r(2 ) = 0.087). Stronger correlations were observed between the RMI and Ep o (r(2) = 0.181) and the TfR (r(2) = 0.191), The results indicate that the RMI represents a cost-effective measurement of erythropoietic act ivity and provides an additional parameter to classify anemic patients into categories of high and low erythropoietic activity, especially i n hypoproductive anemias. (C) 1995 Wiley-Liss, Inc.