Recently a new procedure for measuring serum TSH receptor (TSHR) autoantibody (TRAb) was reported in which the autoantibodies inhibit binding of a human monoclonal thyroid stimulating antibody M22 (labeled with biotin) to TSHR-coated ELISA plate wells. This assay was termed 3rd generation TRAb assay. The aim of the present study was to clinically evaluate the TRAb 3rd generation assay in comparison with the 2nd generation TRAb assay (TRAb-2nd) based on the recombinant human TSH-receptor.
Altogether, 158 patients were analyzed, of whom 84 patients suffered from Graves disease (GD), 34 patients had Hashimotos thyroiditis (HT) and 40 patients had euthyroid nodular thyroid disease (NTD) without signs of autoimmunity. TRAb measurements were performed according to the manufacturers instructions. The TRAb-2nd assay revealed a high sensitivity and specificity as 81 of 84 (96.4%) GD patients were positive. One GD patient had TRAb values within the grey zone (1.01.5 IU/l). All patients with HT and NTD were negative except 6 (17.6%) and 3 (7.5%) cases with TRAb values within the grey zone. On the basis of the TRAb-3rd assay, 77/84 (91.6%) GD patients were TRAb positive. One patient (2.9%) with HT and three cases (7.5%) with NTD were also TRAb positive. The sensitivity of the second and third generation assays were 93% and 84%, while the specificity were 100% and 96.2%, respectively. There was a close correlation (r=0.821, P<0.0001) between TRAb-3rd and TRAb-2nd assays in 84 patients with GD. Problematically, the interassay coefficient of variation was 28.2% using the recommended cut-off limit of 1 IU/l.
Our results indicate that the 3rd generations TRAb assay has a lower sensitivity and specificity compared to the second generation human TSH receptor based TRAb assay.
03 - 07 May 2008
European Society of Endocrinology