Sensitivity, specificity, and predictive value of serum soluble transferrin receptor at different stages of iron deficiency.

This study investigated the efficiency of serum soluble transferrin receptor (sTfR) for assessing body iron status at different stages of iron deficiency. Among 72 patients with advanced iron-deficiency anemia (IDA), the sensitivity and specificity of sTfR (at a diagnostic cutoff of 3.24 mg/L) were 70.8% and 90.6%, respectively, with a positive predictive value of 85.0%. Sensitivities of sTfR in patients at the earliest stage of iron deficiency (n=41) and the intermediate stage of iron-deficient erythropoiesis (n=15) were 21.9% and 26.7%, respectively, at the same cutoff value of sTfR. Serum ferritin concentrations averaged 6.7+/-1.9 microg/L in IDA patients with sTfR <3.24 mg/L, which were significantly above the values in IDA patients with sTfR >or=3.24 mg/L (4.8+/-1.2 microg/L, p<0.05). In healthy controls, blood reticulocyte counts were significantly higher in subjects with sTfR >or=3.24 mg/L than in those with sTfR <3.24 mg/L (0.045+/- 0.013 (10(12)/L) vs 0.034+/- 0.011 (10(12)/L), p<0.05]. In conclusion, sTfR level is not a sensitive indicator for the early or intermediate stages of iron deficiency, although sTfR assay can be a useful aid in the diagnosis of advanced IDA. Serum sTfR concentration has significant relationships with blood reticulocyte counts in healthy subjects and with serum ferritin levels in IDA patients.