An immunoassay for human transferrin.

The laboratory measurement of serum transferrin is a valuable adjunct in the assessment of both iron and protein nutritional status. Conventional assays based on the Fe-binding properties of this protein are tedious to perform, susceptible to Fe contamination, and require volumes of serum that can only be obtained by venous sampling. We describe in this report a two-site enzyme immunoassay (EIA) developed with the use of monoclonal antibodies. Ten microliters serum is diluted 1:20,000 before assay, reflecting a high degree of sensitivity. The variability of this EIA is comparable to conventional colorimetric assays for total iron-binding capacity (TIBC), and excellent correspondence was observed between these methods over a range in TIBC of 150-500 micrograms/dL (27-90 mumol/L). No consistent difference was observed with the EIA when performed on venous and capillary specimens obtained simultaneously. This method will facilitate the evaluation of Fe and protein status in nutritional surveys.