Sensitive assay for thyroglobulin autoantibodies in serum employing polyethylene glycol for precipitation.
A sensitive assay for thyroglobulin autoantibodies (Tg-ab) is described. The assay is based on prolonged incubation of [125I]Tg with serum followed by precipitation of antibody bound [125I]Tg by polyethylene glycol (PEG). The PEG concentration was chosen to give a low precipitation of free [125I]Tg while effectively precipitating Tg-ab-bound [125I]Tg. The lowest reference employed contained 19.5 MRC U/l Tg-ab. This was always different from an incubate without Tg-ab. Tg standard added to samples interfered in the assay giving spuriously low Tg-ab values as in other Tg-ab assays. Tg-ab added to samples was recovered quantitatively. The interassay coefficient of variation was 19.8% and the intra-assay coefficient of variation 11.3%. Only eight of 66 serum samples with various amounts of Tg-ab, measured with the new assay, had levels of Tg-ab detectable by the passive haemagglutination test.
Laurberg
P
P
Second University Clinic of Internal Medicine, Aarhus Kommunehospital, Denmark.
Pedersen
K M
KM
D001323:Autoantibodies / Q000032:analysis*; D011232:Chemical Precipitation; D006386:Hemagglutination Tests; D006801:Humans; D007118:Immunoassay / Q000379:methods; D011092:Polyethylene Glycols / Q000494:pharmacology*; D013954:Thyroglobulin / Q000276:immunology*; D013967:Thyroiditis, Autoimmune / Q000276:immunology
D001323:Autoantibodies; D011092:Polyethylene Glycols; D013954:Thyroglobulin