Assays for thyroid-stimulating hormone receptor antibodies employing different ligands and ligand partners may have similar sensitivity and specificity but are not interchangeable

The best biochemical marker of Graves' disease (GD) is the presence in serum of autoantibodies to the thyroid-stimulating hormone receptor (hTSHR-Ab). The aim of this study was to evaluate the performances of two sensitive hTSHR-Ab assays with a specific focus on the clinical importance of differences in results. Both assays are competitive in nature but employ quite different types of ligands. In the "M22-pTSHR" assay, hTSHR-Ab competes with a labeled monoclonal antibody (M22*) against the thyrotropin (TSH)-receptor for binding to porcine TSH receptors. In the "bTSH-rhTSHR" assay, hTSHR-Ab competes with labeled bovine TSH for binding to recombinant human TSH receptors.