Improved ELISA for Thyroid Microsomal Auto-Antibodies

Abstract

Thyroid microsomal antibodies (TMA) and thyroglobulin antibodies (TGA) are strongly associated with auto-immune thyroid disease. TMA and TGA have been mostly detected by means of either immunofluorescence (IF), tanned red cell haemagglutination (TRCH), or radio-immunoassay (RIA) until the recent development of the enzyme-linked immunosorbent assay (ELISA). The ELISA has not been as extensively used in TMA detection as in the assay for TGA. The RIA method, though more sensitive, is technically and materially very demanding while the TRCH and IF are simpler to perform but are less sensitive. The main problem with the ELISA for the detection of TMA appears to be the interference of TGA present in some test sera reacting with thyroglobulin present as a contaminant in the thyroid microsomal preparation. In this study, we compared the TMA results from an ELISA system designed to eliminate TGA interference with those of IF and TRCH. The ELISA system in which TGA interference was eliminated without concurrent inhibition of the test reaction that gives rise to false negatives was more sensitive than either IF or TRCH. A significant number of samples was falsely reported as negative by both TRCH and IF. The correlation of the degree of positivity between TRCH and ELISA was moderate and was higher than that between ELISA and IF, though both were highly significant. The ELISA technique for TMA detection described here is a more efficient, more sensitive and also more cost-effective system than either TRCH or IF, both of which should now be replaced by ELISA, provided steps are taken to avoid false positives and false negatives.