Enzyme enhanced luminescence immunoassay for the determination of transferrin concentrations in serum

An enzyme enhanced luminescence immunoassay has been developed using the determination of serum transferrin as a model. The assay has been compared with an established radioimmunoassay, the details of which have already been published (Wood, W. G. et al. (1980) Fresenius Z. Anal. Chem. 301, 120). After comparison, the luminescence immunoassay was introduced as the routine method for determining transferrin levels in human serum. The enzyme enhanced luminescence immunoassay uses a pyruvate kinase labelled transferrin as tracer, which, after the antibody-antigen reaction and subsequent bound-free separation, is used to generate adenosine triphosphate (ATP) from adenosine diphosphate(ADP) and phosphoenol pyruvate. The ATP is then monitored with a firefly luciferin-luciferase reagent, using a luminometer as detection system. The intra- and interassay coefficients of variation were under 10% and under 13% respectively in the range 0.6-4.5 g . liter-1. The stability of the lyophilised tracer was in excess of 5 months when stored at 4 degrees C, and the sensitivity of the assay lay under 0.1 micrograms per tube, although the detection limit of this type of assay system has not been fully explored.