A combined enzyme immunoassay (micro-ELISA) technique was established for measuring autoantibodies against thyroglobulin and thyroid microsome, involving the immuno-dot blot technique. Thyroglobulin and thyroid microsome antigens (1 g/L each) prepared from normal thyroids were spotted separately onto nitrocellulose membrane filter discs. Results by this method and those by immunofluorescence correlated well. The percentages of confirmed positives were 30% and 48% and the negatives were 58% and 46% (n = 50) for thyroglobulin and microsome, respectively. Testing these samples by gelatin agglutination gave a high percentage of false positives (up to 20%, n = 128) and hemagglutination testing yielded a high percentage of false negatives (up to 20%, n = 45). The titer of autoantibodies by the micro-ELISA technique was greater than by agglutination. This technique is highly specific and sensitive.
Serum concentrations of thyroid stimulating hormone (TSH) and thyroid autoantibodies in pregnant patients with thyroid disease at various stages of pregnancy were determined by in-house ELISAs. In normal pregnancy, serum TSH levels were significantly elevated (p < 0.05) from 13 weeks of gestation. The normal reference ranges for TSH for the second (0.6-5.0 mIU/l) and third trimester (0.6-5.6 mIU/l) were significantly higher (p < 0.05; p < 0.01 respectively) compared to 0.4-4.5 mIU/l for the first trimester. In pregnant thyroid patients, serum TSH levels correlated highly (p < 0.001) to T4 (r = 0.740), FT4I (r = 0.683) and MicAb (microsomal antibodies) (r = 0.825) but weaker (p < 0.01) to T3 (r = -0.512), FT3I (r = 0.520) and TgAb (thyroglobulin antibodies) (r = 0.618). Thus, measurement of TSH with the highly sensitive ELISA (enzyme linked immunosorbent assay) would form a useful first line test for thyroid dysfunction in pregnancy while measurement of thyroid autoantibodies would aid in the diagnosis of autoimmune hypothyroidism.