How to Supplement Iron in Patients with Renal Anemia

Iron deficiency is a major cause of hyporesponsiveness to erythropoiesis-stimulating agents (ESAs) and is often observed in chronic kidney disease (CKD) patients with anemia. With iron supplementation, ESA doses can be decreased, resulting in lower treatment costs and possibly lower cardiovascular risks that are associated with high-dose ESA therapy. The 2012 Kidney Disease: Improving Global Outcomes Guideline specified ferritin ≤ 500 ng/ml and transferrin saturation (TSAT) ≤ 30% as thresholds of iron parameters for CKD patients. However, long-term safety (in terms of mortality, cardiovascular/infection risk and tissue deposition) of high-dose intravenous iron supplementation with such high target levels of ferritin/TSAT has not been confirmed. Recently, there has been increase in the use of intravenous iron and average ferritin levels in dialysis patients in the United States. Clinical trials conducted so far have been underpowered to conclusively establish the long-term safety of intravenous iron supplementation. Results from observational studies are conflicting, and many experimental studies have even shown negative effects of intravenous iron. Clearly, randomized clinical trials are urgently needed, studying various doses of intravenous iron, with sufficient patient numbers and longer observation periods, to investigate mortality, cardiovascular effects and infection risks of this treatment. Until the long-term safety of iron supplementation at high doses is established, a more prudent decision on iron supplementation with lower target levels of ferritin/TSAT seems reasonable, in light of the decades of experience with ESA that has shown that definitive clinical outcomes have been dissociated from surrogate outcomes (especially hemoglobin concentration).