Serum Transferrin Receptor (sTfR) in the Assessment of Iron Deficiency

Primary Diagnostic Role

sTfR is the preferred biochemical marker for diagnosing iron deficiency, especially when the goal is to differentiate iron‑deficiency anemia from anemia of chronic disease and when ferritin values are unreliable because of inflammation. 1
In patients with chronic inflammatory conditions, chronic kidney disease, or other acute‑phase responses where ferritin may be falsely elevated, sTfR provides valuable diagnostic information that is not confounded by the inflammatory state. [2][1]
The sTfR‑to‑log‑ferritin ratio (TfR‑F Index) offers superior discrimination between iron‑deficiency anemia and anemia of chronic disease compared with either sTfR or ferritin alone. 1
sTfR can detect iron‑deficient erythropoiesis before anemia develops, making it useful for identifying non‑anemic iron deficiency (NAID). However, routine use of this test is not common in many health‑care settings. 1
Elevated sTfR levels are also observed in thalassemias and other hemoglobinopathies, reflecting increased erythropoietic activity unrelated to iron deficiency. 1

Ferritin < 15 µg/L – iron deficiency is confirmed; sTfR testing is unnecessary. 1
Ferritin 15–150 µg/L in the context of chronic disease or inflammation – sTfR measurement or calculation of the sTfR/log‑ferritin ratio should be employed to clarify iron status. [2][1]
Ferritin > 150 µg/L – absolute iron deficiency is unlikely even when inflammation is present; sTfR testing is generally not required. 1

While sTfR identifies iron‑deficient erythropoiesis, it does not by itself distinguish absolute iron deficiency (depleted stores) from functional iron deficiency (restricted iron utilization in chronic disease). The sTfR/log‑ferritin ratio improves this distinction. 1
Different assay platforms use varying cutoff values for sTfR, and these thresholds are population‑specific (varying by age, sex, and ethnicity). Lack of assay standardization limits direct comparison of results across laboratories. (Evidence level not specified)

All statements are based on peer‑reviewed evidence; strength of evidence was not explicitly provided in the source material.