Diagnostic value of iron indices in hemodialysis patients receiving epoetin

Iron deficiency remains a common cause of hyporesponsiveness to epoetin in hemodialysis patients. However, considerable controversy exists regarding the best strategies for diagnosis and treatment.

As part of a multicenter randomized clinical trial of intravenous versus subcutaneous administration of epoetin, we made monthly determinations of serum iron, total iron binding capacity, percentage transferrin saturation, and serum ferritin. If a patient had serum ferritin <100 ng/mL or the combination of serum ferritin <400 ng/mL and a transferrin saturation <20%, he/she received parenteral iron, given as iron dextran 100 mg at ten consecutive dialysis sessions. We analyzed parenteral iron use during the trial, the effect of its administration on iron indices and epoetin dose, and the ability of the iron indices to predict a reduction in epoetin dose in response to parenteral iron administration.

Eighty-seven percent of the 208 patients required parenteral iron to maintain adequate iron stores at an average dose of 1516 mg over 41.7 weeks, or 36 mg/week. Only two of 180 patients experienced serious reactions to intravenous iron administration. Two thirds of the patients receiving parenteral iron had a decrease in their epoetin requirement of at least 30 U/kg/week compared with 29% of patients who did not receive iron (P = 0.004). The average dose decrease 12 weeks after initiating iron therapy was 1763 U/week. A serum ferritin <200 ng/mL had the best positive predictive value (76%) for predicting a response to parenteral iron administration, but it still had limited clinical utility.

Iron deficiency commonly develops during epoetin therapy, and parenteral iron administration may result in a clinically significant reduction in epoetin dose. The use of transferrin saturation or serum ferritin as an indicator for parenteral iron administration has limited utility.