Comparison of Bleomycin-Detectable Iron and Labile Plasma Iron Assays

Abstract

To the Editor: Non–transferrin-bound iron (NTBI)1 is detected in the plasma of patients with diseases in which the transferrin-binding capacity for iron is exceeded by a massive iron overload, such as in certain forms of thalassemia and hemochromatosis, repeated blood transfusions, or bone marrow failure. NTBI may occur in plasma as insoluble polynuclear ferrihydrate species, as Fe(III) citrate or acetate complexes, or bound to certain flavonoids, amino acids, albumin, or modified albumin. Excess iron is harmful because it causes oxidative stress, accumulates in and damages tissues, and enhances the growth of pathogens. Therefore, the measurement of NTBI is of clinical importance, because NTBI may be used as an indicator of systemic iron overload and iron toxicity (1, 2). We compared 2 NTBI assays: a labile plasma iron (LPI) assay that uses desferrioxamine as the iron chelator (3) and a microwell modification of a bleomycin-detectable iron (BDI) assay (2). The BDI assay is an indirect method based on the formation redox-active complexes between NTBI in the sample and the bleomycin reagent. …