Diagnostic accuracy of a new fluoroenzyme immunoassay for the detection of TSH receptor autoantibodies in Graves' disease.

Purpose: Thyrotropin receptor (TSHR) autoantibodies (TRAbs) are a hallmark of Graves' disease (GD). The aim of this study was to evaluate the diagnostic accuracy of a new third generation automatic fluorescence enzyme immunoassay for TRAb measurement in GD, in comparison with two current IMAs.

Methods: Sera of 439 subjects (57 patients with untreated GD, 34 with treated GD, 15 with GD and Graves' orbitopathy, 52 with multinodular non-toxic goiter, 86 with Hashimoto's thyroiditis, 20 with toxic adenoma or toxic multinodular goiter, 55 with non-thyroid autoimmune diseases and 120 normal controls) were tested for TRAbs with the ELiA^™ anti-TSH-R assay (ThermoFischer Scientific, Uppsala, Sweden), the TRAK^™ RIA, Brahms (Thermo Scientific, Hennigsdorf, Germany) and the Immulite^™ TSI assay (Siemens Healthcare, Llanberis, UK).

Results: Sensitivity and specificity of the ELiA™ anti-TSH-R assay, TRAK™ RIA and Immulite™ TSI assay were 94.7% and 99.6, 100 and 98.2%, 100 and 98.2%, respectively. Spearman's coefficient and Passing-Bablok regression showed a satisfactory correlation between EliA™ and TRAK™ [rho: 0.925; 95% CI: 0.883-0-953. Intercept: - 0.875 (95% CI: - 2.411 to 0.194); slope: 1.086 (95% CI: 0.941 to 1.248)], and between ELiA^™ and TSI^™ [rho: 0.947; 95% CI: 0.912 0.969. intercept: 1.085 (95% CI: 0.665 to 2.116); slope 1.315 (95% CI:1.116 to 1.700)].

Conclusions: The diagnostic performance of ELiA^™-TSH-R assay is comparable to that of some current TRAb assays. It may be adopted into clinical practice for the differential diagnosis of hyperthyroidism, to screen for transient hyperthyroidism, and to monitor disease activity and treatment effects.