Clinical applications of the 2nd generation assay for anti-TSH receptor antibodies in Graves' disease. Evaluation in patients with negative 1st generation test.

Detection of autoantibodies to the thyrotropin receptor by radioreceptor assays is largely requested in clinical practice for the diagnosis of Graves' disease and its differentiation from diffuse thyroid autonomy. Additionally, thyrotropin receptor antibodies (TRAb) measurement during antithyroid drug treatment can be useful to evaluate the risk of relapse after discontinuation of the therapy. Nevertheless, some patients affected by Graves' disease are TRAb-negative when a 1st generation assay is used. In this study we evaluated the diagnostic performance of a newly developed 2nd generation TRAb assay in 46 patients with Graves' disease with negative 1st generation TRAb assay results. A control group of 50 Graves' disease patients with positive 1st generation TRAb assay results, 50 patients with Hashimoto's thyroiditis and 50 patients with nodular goiter were also examined. Forty one of 46 patients with Graves' disease with negative 1st generation TRAb assay results showed a positive 2nd generation test. No differences were seen in control groups. In conclusion, the 2nd generation TRAb assay is more sensitive than the 1st generation test and should be used in clinical practice. Long-term prospective studies are needed to evaluate the prognostic role of the 2nd generation TRAb assay in Graves' disease.