Reticulocyte cellular indices: A new approach in the diagnosis of anemias and monitoring of erythropoietic function

Reticulocyte analysis has been extended from the simple enumeration of reticulocytes to precise measurements of mRNA content and of cellular indices such as volume, hemoglobin (Hb) concentration, and content. Assessment of reticulocyte maturity is based on the fluorescence intensity of reticulocytes, which depends on RNA content. The appearance of high fluorescence reticulocytes has been shown to be associated with engraftment in the setting of bone marrow or peripheral stem cells transplantation, although it is still not clear how this parameter can improve quality or cost of care compared with the traditional use of absolute neutrophil counts. Reticulocyte indices have been studied especially in the setting of iron deficiency and functional iron deficiency during recombinant human erythropoietin (r-HuEPO) therapy. Reticulocyte hemoglobin content (CHr) may allow prompt identification of an imbalance between r-HuEPO therapy and iron availability by detecting the presence in reticulocytes of iron-restricted erythropoiesis. Diagnosis of simple iron deficiency can also be achieved in a more cost-effective fashion by using CHr in conjunction with the regular complete blood count (CBC), rather than relying on the traditional biochemical parameters of iron metabolism. Response to therapy of megaloblastic anemia can also be monitored with CHr. These new reticulocyte parameters provide a real-time assessment of the functional state of erythropoiesis.