Nomogram for individualizing supplementary iron doses during erythropoietin therapy in haemodialysis patients.

Abstract

An adequate iron supplement is crucial not only for prompt erythropoiesis but also for the restoration of tissue iron reserves in haemodialysis patients receiving recombinant human erythropoietin (r-HuEPO). An attempt was made to establish a comprehensive nomogram that allows individualization of intravenous (i.v.) iron doses according to patients' body weights, the initial status of tissue iron reserves and desired increases in haemoglobin levels. Clinical and laboratory data retrieved from 95 haemodialysis patients who received r-HuEPO with or without iron supplements for at least 12 weeks were used to construct the nomogram. It was assumed that the administered iron was either incorporated into newly synthesized haemoglobin and tissue iron reserves or eliminated from the body at a constant rate. Tissue iron reserves of the patients were estimated by serum ferritin levels using van Wyck's equation (Kidney Int., 1989, 35, 712). The rate of iron loss in the patients was estimated by the data obtained from 15 of the above patients who exhibited stable haemoglobin levels but decreases in serum ferritin levels with no iron supplements. The validity of the equation was ascertained by comparing the measured serum ferritin levels at the end of r-HuEPO therapy and those predicted by the nomogram. The proposed nomogram was then validated prospectively in 24 haemodialysis patients to determine whether the nomogram-recommended iron doses would increase both haemoglobin and serum ferritin levels within 12 weeks. The mean (+/-SD) iron loss of haemodialysis patients was calculated to be 10.5 +/- 7.4 mg/week. There was a significant correlation (r=0.77, P < 0.001) between the measured serum ferritin levels, an index of tissue iron reserves, at the end of r-HuEPO therapy and those predicted by the equations used for formulating the nomogram. The prospective study indicated that the nomogram-recommended supplementary iron doses attained haemoglobin and serum ferritin levels of > 95 g/L and >100 microg/L in 79 and 50% of the patients, respectively, within 12 weeks. The present nomogram may be useful for individualizing supplementary i.v. iron doses for haemodialysis patients undergoing r-HuEPO therapy.