Single values of serum transferrin receptor and transferrin receptor ferritin index can be used to detect true and functional iron deficiency in rheumatoid arthritis patients with anemia

OBJECTIVE: To elucidate the use of serum transferrin receptor (sTfR) to distinguish between iron-deficiency anemia (IDA) and anemia of chronic disease (ACD), and to establish an improved scheme to identify functional iron deficiency (FID) in rheumatoid arthritis (RA) patients with anemia. METHODS: We studied 30 anemic RA patients whose iron status was confirmed by bone marrow examination and determination of the sTfR level, serum ferritin level, and sTfR-log ferritin index (TfR-F Index). All patients with diminished or exhausted iron stores (n = 18) received oral iron supplementation. RESULTS: Baseline values of sTfR and the TfR-F Index predicted the response correctly in all patients who received supplementation treatment and were normal in 10 of 11 patients with normal initial iron stores (ACD). CONCLUSION: The results of this study elucidate the roles of sTfR and the TfR-F Index in the differential diagnosis between IDA and ACD and provide direct evidence that these parameters are useful in detecting FID, irrespective of the concurrent iron storage status.