Relative Contributions of Body Iron Status and Uremia Severity to Anemia in Patients with Advanced Chronic Renal Failure

Abstract

Anemia in chronic renal failure is predominantly caused by diminished erythropoietin synthesis by diseased kidneys. While iron deficiency is often stated as a cause of anemia in chronic renal failure prior to end-stage renal disease, its relative contribution is debated. It is speculated that rather than frank ‘iron deficiency’, many patients with chronic renal failure may indeed have impaired utilization of iron. We analyzed 139 consecutive patients with chronic renal failure starting maintenance hemodialysis to determine the relationship between hematocrit, measures of renal function (blood urea nitrogen and serum creatinine concentration), and measures of iron availability (serum transferrin saturation, serum iron level and serum ferritin). The 139 study subjects (60 men, 79 women) comprised 116 blacks (83%), 15 hispanics (11%), and 8 whites (6%) of a mean age 56 ± 15 years. Only 23 (17%) of 139 subjects had positive hemoccult stool test for blood. Their mean hematocrit was 24 ± 4.5%, mean blood urea nitrogen concentration was 121 ± 38, mean serum creatinine concentration was 12.6 ± 5.2 mg/dl, mean serum transferrin saturation was 22 ± 14%, mean serum ferritin level was 235 ± 194 U/l, mean serum iron level was 55 ± 40 U/l, and mean total iron binding capacity was 254 ± 93%. Multiple regression analysis with hematocrit as the outcome variable, and blood urea nitrogen level, serum creatinine concentration, serum albumin concentration, serum transferrin saturation, and serum ferritin level as the independent variables, showed an inverse correlation between hematocrit and serum creatinine concentration (p = 0.002). We conclude that in patients with chronic renal failure starting uremia therapy, anemia does not correlate with any of the commonly measured indices of body iron stores. We infer that impaired utilization of iron may be a significant factor in the anemia of chronic renal failure.