Quantitation of human serum antithyroglobulin antibodies by a two-site radioimmunoassay.

A two-site solid-phase radioimmunoassay for measuring serum antithyroglobulin antibodies applicable to human serum is described. The sequential steps of the procedure include the adsorption of thyroglobulin (Tg) on polystyrene tubes and the binding of the antithyroglobulin antibody to solid phase followed by the fixation of labelled thyroglobulin. The optimal experimental conditions for the adsorption of unlabelled Tg, the uptake of the antibodies and the fixation of labelled Tg have been defined. The test is specific for antithyroglobulin antibody and its reproducibility and precision are satisfactory. The radioassay showed a good correlation with the hemagglutination method and, also, was found to be more sensitive. Levels of antithyroglobulin IgG in positive sera ranged from 0.3 microgram/ml to several mg/ml. In contrast to the double antibody radioimmunoassay for antithyroglobulin antibodies, this solid-phase radioassay is easier to perform; moreover, it is relatively independent of the quality, the purity and the specific activity of the tracer.