A clinical comparison of the enzyme-linked immunosorbent assay (ELISA) and haemagglutination (TRC) in the routine detection of antithyroglobulin antibodies.

The enzyme-linked immunosorbent assay (ELISA) has been proposed as an alternative to haemagglutination (TRC) in the routine examination of sera for autoantibodies such as thyroglobulin antibody (Anti-Tg). However, very few clinical comparisons of the two tests, incorporating matched controls and an independent standard, have so far been published. We have compared the performance of ELISA and TRC as screening procedures in 814 patients referred to our autoimmune profile laboratory with clinically suspected thyrotoxicosis, Hashimoto's thyroiditis or myxoedema. Radioimmunoassay (RIA) was used as the independent standard, and the normal range for each test was established from 100 carefully age and sex-matched controls. Sixty-five % of the sera were negative in all three tests. The results from ELISA and RIA were very similar (r = 0.88, P less than 0.001), with no major discrepancy. TRC, however, was negative in 101 (40.2%) of 251 RIA positive sera (r = 0.61, P less than 0.001) and in 118 (44.2%) or 267 ELISA positive patients (r = 0.69, P less than 0.001). Some of the TRC negative sera were strongly RIA and ELISA positive. ELISA is fully quantitative, cheap, and was found to be more accurate than TRC in identifying anti-Tg positive individuals. It has the potential to replace TRC in the routine screening of sera for anti-Tg antibodies.