What is the role of soluble transferrin receptor in iron status assessment when inflammation is present?

• A. It directly measures ferritin.
• B. It is used to monitor ferritin over time.
• C. It indicates inflammatory activity regardless of iron status.
• D. It helps distinguish iron deficiency from inflammation when ferritin is inconclusive.

Answer: (D)

The key idea is that ferritin is a good indicator of iron stores but is also an acute‑phase protein that rises with inflammation, which can mask iron deficiency. Soluble transferrin receptor (sTfR) reflects cellular iron demand for erythropoiesis and tends to rise when iron is deficient, but it is much less influenced by inflammatory processes. Because of this, sTfR can help untangle a ferritin that’s elevated from inflammation from true iron deficiency. When ferritin is inconclusive due to inflammation, measuring sTfR (often using the sTfR/log ferritin index) helps determine whether iron deficiency is present: a high sTfR (or a high index) points to iron deficiency despite high ferritin, whereas a normal or low sTfR with high ferritin suggests inflammation with adequate iron stores.