Evaluation of RBC ferritin and reticulocyte measurements in monitoring response to intravenous iron therapy

Intravenous (IV) iron therapy can reduce erythropoietin (EPO) requirements in dialysis patients. Monitoring this response accurately is difficult, Estimation of red blood cell ferritin (RBCFer) and reticulocyte indices may give additional valuable information about iron availability to the erythroblasts (erythron). We evaluated the use of RBCFer, mean hemoglobin content of reticulocytes (CHr), and mean hemoglobin concentration of reticulocytes (CHCMr) in a prospective, nonblinded study of 22 hemodialysis patients (16 men and six women with a mean age of 62 years [range, 24 to 80 years]), All patients had an initial serum ferritin of less than or equal to 60 mu g/L, Patients with features known to produce EPO resistance and underlying bleeding/hematologic disorders were excluded, Patients were established on subcutaneous EPO and given IV iron therapy, The mean hemoglobin level remained constant throughout the study (P = 0.087), Serum ferritin and RBCFer increased significantly (P < 0.001 and 0.015, respectively) while a reduction in transferrin saturation became significant at the end of the study (P = 0.0047), A sharp increase in reticulocytes occurred in the first 14 days after commencement of IV iron, and there was an initial decrease in the percentage of hypochromic RBCs, An early decline in RBCFer was apparent. CHr increased with IV iron, indicative of increased iron supply to the developing erythron. Measurement of RBCFer and CHr provide evidence of increased iron supply for erythropoiesis during IV iron therapy. These measures help identify patients with functional iron deficiency and allow more accurate monitoring of response to IV iron therapy. (C) 1997 by the National Kidney Foundation, Inc.