Comparison of some different methods for analysis of thyroid autoantibodies: Importance of thyroglobulin autoantibodies

Blood samples from 141 children and adolescents were used to evaluate diffe rences between commercial kits and radioimmunoassay (RIA) methods for detec ting thyroid autoantibodies. Thyroglobulin autoantibodies (Tg-Ab) were anal yzed with a hemagglutination kit and a RIA; thyroid peroxidase autoantibodi es (TPO-Ab) were measured with a gelagglutination assay and a RIA. The resu lt; of the antibody tests were compared with thyroid function tests (triiod othyronine [T-3] thyroxine [T-4], thyrotropin [TSH]) and with the results o f ultrasound of the thyroid in antibody-positive patients. The correlation of antibody levels between the two methods was higher for TPO-Ab than for T g-Ab. Moderate to high levels of TPO-Ab correlated to elevated TSH levels. Auto immune thyroiditis (AIT) was found in 6 of the 141 children. The RIA-b ased thyroglobulin assay was the only test that identified autoantibodies i n all 6 cases. in contrast, the hemagglutination kit thyroglobulin assay fa iled to identify 4 of the 6 AIT cases.