Soluble transferrin receptor: a discriminating assay for iron deficiency.

The distinction between iron deficiency anaemia (IDA) and the anaemia that accompanies infection, inflammation or malignancy, commonly termed the anaemia of chronic disease (ACD), is often difficult, as the conventional laboratory indices of iron status are often influenced by acute phase responses. In recent years, the soluble transferrin receptor (sTfR) has been introduced as a sensitive, early and highly quantitative new marker of iron depletion, increasing in proportion to tissue iron deficit. Unlike conventional laboratory tests, the sTfR is not an acute phase reactant and remains normal in patients with chronic disease. In this study TfR concentrations were compared with the gold standard of iron stores, bone marrow iron. The sTfR concentration was shown to be the most efficient test in predicting bone marrow iron stores in 20 patients with ACD (75% efficiency) and in 18 patients with rheumatoid arthritis (RA) (94% efficiency). Measurement of sTfR may be a useful addition in the differential diagnosis of ACD and IDA.