Is soluble transferrin receptor a useful marker in early stage iron deficiency?

Background and aims: Soluble transferrin receptor (sTfR) is a recent test used to assess iron status and diagnose iron deficiency. Unlike Ferritin, it does not change during acute phase responses. The aim was to (1) review literature on sTfR in the assessment of early stage iron deficiency and (2) report baseline sTfR from a recent randomised controlled trial. Methods: A search from earliest record to June 2013 located peer-reviewed studies using sTfR as a marker of early stage iron deficiency. Reference ranges and sTfR values were tabulated and compared with results from a current trial conducted at the University of Newcastle, Australia. Results: Of eight studies on early stage iron deficiency (iron storage depletion) that measured sTfR, seven different assays were used. Baseline results from the current trial demonstrated a significant difference in mean sTfR level between iron deficient and iron replete participants, (0.99 ± 0.20, 1.26 ± 0.36, p < 0.01). However no participants (n = 119) had sTfR levels outside the reference range (0.9–2.3 mg/L). Conclusions: While sTfR levels were higher in early stage iron deficiency, defined by low Ferritin, the reference range was not useful in identifying early stage iron deficiency. Multiple assays using varying reference ranges make between study comparisons difficult