Sensitive time-resolved fluorimetric immune-complex-transfer immunoassay for antithyroglobulin IgG in serum

A sensitive time-resolved fluorimetric immune-complex-transfer immunoassay for antithyroglobulin IgG in serum is described. Antithyroglobulin IgG in test serum was reacted with dinitrophenyl europium ion-labeled thyroglobulin. The complex formed of antithyroglobulin IgG and dinitrophenyl europium ion-labeled thyroglobulin was trapped onto two polystyrene balls coated with affinity-purified rabbit antidinitrophenyl bovine serum albumin IgG. The polystyrene balls were washed to eliminate nonspecific IgG in the test serum, and the complex was eluted from the polystyrene balls with dinitrophenyl-L-lysine and transferred to two polystyrene balls coated with affinity-purified rabbit antihuman IgG gamma-chain IgG. Europium ion bound to the polystyrene balls was measured by time-resolved fluorimetry. Antithyroglobulin IgG was demonstrated in all patients with Graves' disease and all patients with chronic thyroiditis. This immunoassay was more sensitive than the conventional enzyme immunoassay and less time-consuming than the previously described immune-complex-transfer enzyme immunoassays, although there were larger assay variations.