Variations in erythropoiesis and serum ferritin during erythropoietin therapy for anaemia of end-stage renal disease

In order to study the relationship between erythropoiesis and serum ferritin (SF) during erythropoietin (rHuEPO) therapy in the anaemia of end-stage renal disease (ESRD), 19 patients were followed without iron supplementation and at a fixed dose of the drug (40 U/kg). Twelve patients failed to attain the target haemoglobin (Hb) value, 7 of whom due to the appearance of iron deficiency. Erythropoiesis, as measured by the serum transferrin receptor concentration, increased from 12 to 120% of the basal value. This increment was not constantly associated with a proportional rise of Hb or reticulocyte count. SF decreased exponentially from a median value of 221 μg/dl (range 42-470) to a median value of 54 μg/dl (range 20-172). Halving of the basal SF value (SF-T50) was reached at the 18th-95th day of therapy (median = 43), representing a iron shift of 3.4-11.6 mg/day (median = 5.4). SF-T50 was not correlated with the Hb increase, but with that of erythropoiesis (r = 0.78; p = 0.003). The minimum SF (MSF) value attained was not correlated with the appearance of iron deficiency. The conclusion is that the rate of SF decrease during rHuEPO in ESRD is a reliable measure of iron mobilisation for erythropoiesis, but not for haematologic response. The MSF value reached during therapy is not representative of available iron for erythropoiesis.