[Radioimmunological assay for antithyroglobulin antibodies, with the use of staphylococcal protein A as separating agents (author's transl)].

The staphylococcal cell wall protein A is known to bind specifically and rapidly to most of human immunoglobulin G. We have utilised this immunoadsorbent in a radio-immunoassay for antithyroglobulin antibodies (anti-Tg), to separate autoantibodies-125I thyroglobulin complexes from free 125I thyroglobulin (125I Tg). There was no specific precipitation of 125I Tg in the presence of 95,6% of sera from normal subjects (N = 45). In graves' disease, 56/65 hyperthyroid patients sera were positive, and so were 12/13 sera from patients with primary hypothyroidism. This assay showed a good correlation with the second antibody method, while much more rapid and slightly more sensitive. Compared with the new assay, the red cell agglutination test exhibited a high frequency of false negative results. This rapid, sensitive and inexpensive method provide an easy and reliable tool to screen sera acceptable for thyroglobulin measurement.