Diagnostic Availability of the Soluble Transferrin Receptor in Old Patients with Iron Deficiency Anemia and Anemia of Chronic Renal Failure

Lee, Myung Hee

Abstract

BACKGROUND
The diagnostic efficiency of soluble transferrin receptor (sTfR) was investigated to detect iron deficiency among old patients with iron deficiency anemia (IDA) and anemia of chronic renal failure (CRF). METHODS: Twenty five patients with uncomplicated IDA [mean corpuscular volume (MCV) <80 fL, ferritin <23.8 g/L, group I], 21 patients with atypical anemia [MCV <80 fL, ferritin > or =23.8 g/L, group II, n=5 ; MCV > or =80 fL, ferritin <23.8 g/L, group III, n=16], 85 patients with anemia of chronic renal failure [MCV > or =80 fL, ferritin > or =23.8 g/L, group IV], and 20 normal controls were included in the study. The levels of sTfR, hemoglobin (Hb), MCV, serum ferritin, serum iron (Fe), total iron binding capacity (TIBC), c-reactive protein (CRP) and calculated transferrin saturation (% sat) of each group were compared. The correlations between iron parameters and the sTfR levels were investigated in each group. RESULTS: The mean values of sTfR were significantly higher in group I (5.3+/-3.5 mg/L), group II, (2.6+/-1.1 mg/L) and group III (2.0+/-0.9 mg/L) than in normal controls (1.2+/-0.3 mg/L) and group IV (1.2+/-0.7 mg/L). The proportion of patients with sTfR level higher than the upper normal limit (1.74 mg/L) was 37.4% (100% of group I, 80% of group II, 56% of group III, and 13% of group IV), and that with ferritin level lower than 23.8 g/L was 31.3% (41/131). The proportion of patients with normal sTfR and decreased ferritin was 5.3% (7/131) and that with normal ferritin and increased sTfR was 11.5% (15/131) A good correlation (r>0.800) was observed between Fe and % sat in all patients, microcytic anemic patients, and patients with anemia of CRF; between ferritin and CRP in microcytic anemia patients (r=0.800); and between serum iron and MCV in all patients (r=0.615). A good inverse correlation was observed between ferritin and TIBC (r=-0.649) and between CRP and TIBC (r=-0.614) in microcytic anemic patients only. CONCLUSIONS: Because the sTfR level was significantly higher in microcytic anemic patients and anemic patients with a relatively low ferritin than in anemic patients of CRF and normal controls, especially in more advanced IDA, and because the sTfR detected more IDA patients than ferritin did, thesTfR is the most useful marker expressing functional iron deficiency without being affected by CRP.