Thyroid-blocking immunoglobulins (TBI) are present in 10%–15% of patients with autoimmune thyroid disease (AITD). TBI affect thyroid function. The analytical performance of a novel TBI bioassay was evaluated.
Sera from AITD patients were tested with a cell-based TBI reporter bioassay (Thyretain®) with the expression of a luciferase transgene as readout and a new “Turbo™” TBI bioassay with a readout based on a cyclic AMP-activated luciferase. All samples were also run on two TSH-R binding immunoassays. A Passing–Bablok regression, a Bland–Altman plot, and user/lot comparisons were performed. In addition, dose–response curves for Turbo and Thyretain were fitted using serial dilutions, and half-maximal and 80% inhibitory concentrations (IC50/IC80) were compared.
Of 1,011 unselected AITD patients, 131 patients (212 samples) were TBI positive. Of the 212 samples, 149 (70.3%), 47 (22%), and 16 (7.5%) were hypothyroid, euthyroid, and hyperthyroid, respectively. The three thyrotropin receptor antibody (TSH-R-Ab) assays were negative in 90 controls devoid of autoimmune thyroid disorders. In contrast, the Turbo cyclic adenosine 3′,5′-monophosphate (cAMP) TBI, Thyretain TBI, and the binding assays detected TBI in 212 (100%), 168 (79%), and 138/180 (65%) samples, respectively (
The novel, easy-to-perform, rapid, and reliable Turbo TSH-R blocking bioassay detected significantly more TBI than the established immunoassays, emphasizing its higher analytical performance and clinical utility in the management of patients with AITD.