[Detection of the antithyroglobulin antibody precipitated with polyethylene glycol (PEG) (author's transl)].

It is well known that the antithyroglobulin (anti-Tg) antibody plays an important role in the pathogenesis of autoimmune thyroiditis (chronic thyroiditis). The anti-Tg antibody is detected by double diffusion in agar gel, the fluorescent antibody technique and the tanned red cell haemagglutination test (TRC). The most widely used method is the TRC test, but it is negative in about 30 percent of the patients with chronic thyroiditis. In this paper, we have reported the detection of the anti-Tg antibody in serum using a modified Farr's method. In our method, PEG was used instead of ammonium sulfate to precipitate the immune complex formed in vitro between labelled Tg and the autoantibody. Percent 125I-Tg precipitated was 4.7 +/- 3.1 percent in normal controls; 20.4 +/- 11.4 percent in TRC negative sera were detected by this method. A good correlation was found between TRC titer and percent 125I-Tg precipitated by the PEG method in patients with chronic thyroiditis. By this method, the anti-Tg antibody was also detected in the sera of rabbits immunised with human Tg earlier than that detected by the TRC and double diffusion tests. The sensitivity and simplicity of this method provide a useful tool in detecting the anti-Tg antibody in clinical as well as in experimental work.