Performance of two agglutination techniques in the detection of thyroid antibodies and assessment of their clinical significance.

Two clinically most widely used agglutination tests, Thymune and Serodia distributed by Wellcome and Fjirebio/Ames, respectively, to determine thyroid autoantibodies were compared. The Serodia tests seemed to be considerably more sensitive than the corresponding Thymune tests; first, Serodia tests resulted in several new positive samples and second, 16% and 30% of positive thyroglobulin and thyroid microsomal antibodies by Serodia resulted in at least 16 times higher titres, respectively. Over 300 healthy blood donor sera were used to determine the occurrence of thyroid autoantibodies in normal population. Titre limits of 400 and 6400 in anti-thyroglobulin and anti-microsomal antibodies were adapted for clinical use, respectively, even though the results suggested that the lower titre limits could be applied for males and subjects younger than 40 years. These defined titre limits were applied to examine randomly selected clinical patient material gathered during 1 year. The main patient groups identified included patients with chronic thyroiditis, thyroid malignancy, diabetes. Graves' disease and rheumatoid diseases as well as patients with vaguely defined clinical conditions. Without the aid of antithyroglobulin antibodies only one patient with chronic thyroiditis would have been missed if thyroid microsomal antibodies were used alone. Thus, in general clinical practise thyroid microsomal antibodies can be used as a sole diagnostic test for autoimmune thyroid diseases.