Clinical utility of the soluble transferrin receptor and comparison with serum ferritin in several populations

TLDR

The study compared soluble transferrin receptor and ferritin concentrations across diverse clinical settings to determine their effectiveness in identifying iron deficiency. Researchers measured sTfR and ferritin levels in anemic patients, 267 outpatient samples, and 112 medical students to evaluate diagnostic performance. sTfR detected iron deficiency with 92 % sensitivity and 84 % specificity in anemic patients, outperforming ferritin (≤12 µg/L) which had 25 % sensitivity and 98 % specificity, though a ≤30 µg/L cutoff raised ferritin sensitivity to 92 %; in outpatient and student cohorts the two tests agreed 73–91 % of the time, indicating sTfR offers limited additional information except as an adjunct when ferritin is elevated by inflammation.

Abstract

Soluble transferrin receptor (sTfR) and ferritin concentrations were measured in a variety of clinical settings to compare the ability of these two tests to identify iron deficiency. Among 62 anemic patients who either had a bone marrow aspirate performed or had a documented response to iron therapy, the diagnostic sensitivity and specificity of sTfR (at a diagnostic cutoff of > 2.8 mg/L) were 92% and 84%, respectively, with a positive predictive value of 42% in this population. Ferritin (< or = 12 microg/L) had a sensitivity of 25% and a specificity of 98%. However, the sensitivity and specificity of ferritin could be improved to 92% and 98%, respectively, by using a diagnostic cutoff value of < or = 30 microg/L, resulting in a positive predictive value of 92%. Ferritin and sTfR were also measured in 267 outpatient samples and 112 medical students. In the outpatient group, the two tests agreed in 73% of the samples; however, 25% of the samples had ferritin values > 12 microg/L and increased sTfR. Among the medical students, there was 91% agreement between the two tests, but 7% of the samples had ferritin < or = 12 microg/L and normal sTfR. Together, these data suggest that measurement of sTfR does not provide sufficient additional information to ferritin to warrant routine use. However, sTfR may be useful as an adjunct in the evaluation of anemic patients, whose ferritin values may be increased as the result of an acute-phase reaction.