Erythropoiesis-stimulating agent hyporesponsiveness in end-stage renal disease patients

Approximately 5-10% of patients with end-stage renal disease (ESRD) exhibit hyporesponsiveness to erythropoiesis-stimulating agents (ESAs), defined as a continued need for higher than 300 IU/kg/week doses of epoetin or a 1.5 mg/kg/week dose of darbepoetin. ESA hyporesponsiveness contributes to the morbidity, mortality and health-care economic burden of ESRD patients. The most common causes of ESA resistance are absolute or functional iron deficiency and inflammation. Maintaining adequate iron stores is clearly accepted as the most important strategy for reducing the ESA requirement and for enhancing ESA efficacy. Recent clinical studies have shown that iron administration to ESRD patients is associated with an increased risk of infection and atherosclerosis. ESA hyporesponsiveness due to chronic inflammation in ESRD patients has been reported to be improved by a number of interventions, including the use of biocompatible hemodialysis membranes, ultrapure dialysate, ascorbic acid therapy, vitamin E supplementation, and statin therapy. Other causes of ESA hyporesponsiveness include inadequate dialysis, hyperparathyroidism, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, primary bone marrow disorders, myelosuppressive agents, hemoglobinopathies, hemolysis, and hypersplenism. This article summarizes the common causes of ESA hyporesponsiveness and the proposed therapeutic interventions.