Clinical Journal of the American Society of Nephrology Iron Deficiency in the 2006 K/DOQI ERA: Diagnosis and Management

More than a Decade of Experience and Still No Consensus: Controversies in Iron Therapy

Besarab, A. — 2006-08-30

Assessing Iron Status: Beyond Serum Ferritin and Transferrin Saturation

Wish, J. B. — 2006-08-30

The increasing prevalence of multiple comorbidities among anemic patients with chronic kidney disease has made the use of serum ferritin and transferrin saturation more challenging in diagnosing iron deficiency. Because serum ferritin is an acute-phase reactant and because the inflammatory state may inhibit the mobilization of iron from reticuloendothelial stores, the scenario of patients with serum ferritin >800 ng/ml, suggesting iron overload, and transferrin saturation <20%, suggesting iron deficiency, has become more common. This article revisits the basis for the Kidney Disease Outcomes Quality Initiative recommendations regarding the use of serum ferritin and transferrin saturation in guiding iron therapy, then explores some of the newer alternative markers for iron status that may be useful when serum ferritin and transferrin saturation are insufficient. These newer tests include reticulocyte hemoglobin content, percentage of hypochromic red cells, and soluble transferrin receptor, all of which have shown some promise in limited studies. Finally, the role of hepcidin, a hepatic polypeptide, in the pathophysiology of iron mobilization is reviewed briefly.

The Fascinating but Deceptive Ferritin: To Measure It or Not to Measure It in Chronic Kidney Disease?

Kalantar-Zadeh, K., Kalantar-Zadeh, K., Lee, G. H. — 2006-08-30

Although the emergence of erythropoiesis-stimulating agents has revolutionized the anemia management of chronic kidney disease (CKD) in the past two decades, strategies to assess iron (Fe) status and to provide Fe supplementation have remained indistinct. The reported cases of hemochromatosis in dialysis patients from the pre–erythropoiesis-stimulating agent era along with the possible associations of Fe with infection and oxidative stress have fueled the "iron apprehension." To date, no reliable marker of Fe stores in CKD has been agreed on. Serum ferritin continues to be the focus of attention. Almost half of all maintenance hemodialysis patients have a serum ferritin >500 ng/ml. In this ferritin range, Fe supplementation currently is not encouraged, although most reported hemochromatosis cases had a serum ferritin >2000 ng/ml. The moderate-range hyperferritinemia (500 to 2000 ng/ml) seems to be due mostly to non–Fe-related conditions, including inflammation, malnutrition, liver disease, infection, and malignancy. Recent epidemiologic studies have shown that a low, rather than a high, serum Fe is associated with a poor survival in maintenance hemodialysis patients. In multivariate adjusted models that mitigate the confounding effect of malnutrition-inflammation, serum ferritin <1200 ng/ml and Fe saturation ratio in 30 to 50% range are associated with the greatest survival in maintenance hemodialysis patients. Although ferritin is a fascinating molecule, moderate hyperferritinemia is a misleading marker of Fe stores in patients with CKD. It may be time to revisit the utility of serum ferritin in CKD and ask ourselves whether its measurement has helped us or has caused more confusion and controversy.

Acute Injury with Intravenous Iron and Concerns Regarding Long-Term Safety

Bishu, K., Agarwal, R. — 2006-08-30

Intravenous iron is widely used to maintain adequate iron stores and prevent iron deficiency anemia in patients with chronic kidney disease, yet concerns remain about its long-term safety with respect to oxidative stress, kidney injury, and accelerated atherosclerosis, which are the subjects of this review. Three parenteral iron formulations are available for use in the United States: Iron dextran, iron gluconate, and iron sucrose. Iron dextran, especially the high molecular form, has been linked with anaphylactoid and anaphylactic reactions, and its use has been declining. A portion of intravenous iron preparations is redox-active, labile iron available for direct donation to transferrin. In vitro tests show that commonly available intravenous iron formulations have differing capacities to saturate transferrin directly: Iron gluconate > iron sucrose > iron dextran. Intravenous iron treatment produces oxidative stress, as demonstrated by increases in plasma levels of lipid peroxidation products (malondialdehyde), at a point that is much earlier than the time to peak concentration of catalytically active iron, suggesting a direct effect of iron sucrose on oxidative stress. Furthermore, iron sucrose infusion produces endothelial dysfunction that seems to peak earlier than the serum level of free iron. Intravenous iron sucrose infusion also has been shown to produce acute renal injury and inflammation as demonstrated by increased urinary albumin, enzyme (N-acetyl-ß-glucosaminidase), and cytokine (chemokine monocyte chemoattractant protein-1) excretions. Although the long-term dangers of intravenous iron are unproved, these data call for examination of effects of intravenous iron on the potential for long-term harm in patients with chronic kidney disease.

Parenteral Iron Compounds: Potent Oxidants but Mainstays of Anemia Management in Chronic Renal Disease

Zager, R. A. — 2006-08-30

Ferric iron (Fe)–carbohydrate complexes are widely used for treating Fe deficiency in patients who are unable to meet their Fe requirements with oral supplements. Intravenous Fe generally is well tolerated and effective in correcting Fe-deficient states. However, the complexing of Fe to carbohydrate polymers does not block its potent pro-oxidant effects; systemic free radical generation and, possibly, tissue damage may result. The purpose of this review is to (1) underscore the capacity of currently used parenteral Fe formulations to induce oxidative stress, (2) compare the severity of these oxidant reactions with those that result from unshielded Fe salts and with each other, and (3) speculate as to the potential of these agents to induce acute renal cell injury and augment systemic inflammatory responses. The experimental data that are reviewed should not be extrapolated to the clinical setting or be used for clinical decision making. Rather, it is hoped that the information provided herein may have utility for clinical hypothesis generation and, hence, future clinical studies. By so doing, a better understanding of Fe's potential protean effects on patients with renal disease may result.