Immunological measurement of transferrin compared with chemical measurement of total iron-binding capacity.

Because of uncertainty as to the molecular weight of transferrin, a previous comparison [Von der Heul et al., Clin. Chim. Acta 38, 347 (1972)] between transferrin content of serum and total iron-binding capacity cannot be definitive. We found a conversion factor for expressing the maximum amount of iron bound by 1 mg of transferrin. We compared the resulting calculated value with values obtained by three other methods for measuring total iron-binding capacity. We agree with the previous observation that the latter, as measured radioisotopically, give higher results than would be judged from the transferrin content but the same as those for two chemical methods. The diffusion rate of transferrin in agar was the same irrespective of the degree of iron saturation. Serum transferrin concentrations were low in patients with anemia resulting from malignancy, chronic disorders, and cirrhosis of the liver, and high or normal in patients with iron deficiency anemia and in pregnant women or women who were taking birth-control pills. Measurement of transferrin concentration can be used to distinguish iron deficiency anemia from anemia resulting from chronic disorders, but offers no advantages over existing methods for estimating total iron-binding capacity.