Diagnosis of iron deficiency in chronic renal failure

The cause of anemia in chronic renal failure is multifactorial. Decreased erythropoietin (EPO) production is the main pathogenetic factor, but iron deficiency is the primary cause of unresponsiveness to EPO therapy. The diagnosis of iron deficiency in patients with chronic renal failure is difficult. We assessed the sensitivity and specificity of serum ferritin, total iron-binding capacity, transferrin saturation index, erythrocyte ferritin, and serum transferrin receptor in 63 patients with chronic renal failure undergoing dialysis (47 men, 16 women) with iron deficiency anemia. They were selected on the basis of clinical stability and absence of factors that may interfere with iron metabolism. None of the patients had received intravenous iron therapy or recombinant human erythropoietin (rHuEPO). Bone marrow biopsy with iron staining was the reference standard for iron stores. The receiver operating characteristic (ROC) curve and the area under the curve were calculated to assess the sensitivity and specificity of iron metabolism parameters. The parameter with the largest area under the ROC curve was serum ferritin (0.83). A cut point of 121 microgram/L showed a sensitivity and a specificity of 75%. The areas under the ROC curves of serum transferrin receptor and erythrocyte ferritin were 0.69 and 0.68, respectively. The remaining parameters showed areas under the ROC curve less than 0.65. Although serum transferrin receptor and erythrocyte ferritin may be acceptable markers for iron deficiency in stable chronic renal failure patients, serum ferritin level continues to be the most reliable diagnostic parameter. Transferrin saturation index is not a reliable parameter for the diagnosis of iron deficiency in stable patients not treated with rHuEPO.