Sensitive radioimmunological screening test for antithyroglobulin autoantibodies

The test described here was designed as a screening test to be used in conjunction with the radioimmunoassay for human thyroglobulin. Anti-thyroglobulin autoantibodies, when present even in low concentrations, interfere with thyroglobulin determination. A 30-min incubation allows binding of 125I-thyroglobulin to endogenous anti-thyroglobulin autoantibodies. A subsequent 2-h incubation with goat anti-human gamma-globulin causes precipitation of such complexes. The immunoprecipitable radioactivity reflects the binding capacity of the sample for 125I-labeled thyroglobulin. Samples that are devoid of autoantibodies, and are therefore suitable for valid thyroglobulin determinations, bind less than 6% of the radiolabeled thyroglobulin. The sensitivity of this radioimmunoassay exceeds that of the tanned-erythrocyte hemagglutination test.