Serum hepcidin‐25 may replace the ferritin index in the Thomas plot in assessing iron status in anemic patients

Introduction: Biochemical markers of iron deficiency do not distinguish iron‐deficient anemia (IDA) from the anemia of chronic disease (ACD) and the combined state of ACD/IDA. Serum hepcidin‐25 might be a marker resolving this problem. We investigated the extent to which serum hepcidin‐25 enables the differentiation of the states above in comparison with the ferritin index plot, the so‐called Thomas plot [soluble transferrin receptor (sTfR)/log ferritin and the reticulocyte hemoglobin content (CHr)]. Methods: Serum hepcidin‐25 was determined in 155 anemic patients who were classified as having latent iron deficiency (latent ID), IDA, ACD, or ACD/IDA using the ferritin index plot (Thomas plot). Hepcidin‐25 was determined using an isotope‐dilution micro‐HPLC‐tandem mass spectrometry method. The ability to discriminate among these states based on serum hepcidin‐25 alone or in combination with the CHr was evaluated in a receiver operating characteristic curve analysis and a comparison with the recently established ferritin index plot. Results: Serum hepcidin‐25 correlated with ferritin and the ferritin index. Use of a hepcidin‐25 cutoff level of ≤4 nmol/l allowed the differentiation of IDA from ACD and ACD/IDA. Furthermore, the discrimination of ACD/IDA from ACD required combination with CHr in a new plot (hepcidin‐25 and the CHr). The hepcidin‐25 plot and the ferritin index plot showed a good correspondence in the differentiation of iron states in patients with anemia. Conclusion: Patients with IDA can be differentiated from ACD and ACD/IDA but not ACD from ACD/IDA based on hepcidin‐25 alone. The combination of hepcidin‐25 with CHr in the hepcidin‐25 plot was useful for the differentiation of the states above.