Novel chimeric thyroid-stimulating hormone-receptor bioassay for thyroid-stimulating immunoglobulins

Area of Science:

• Endocrinology
• Immunology
• Biotechnology

Background:

• Thyroid-stimulating immunoglobulins (TSI) are crucial functional biomarkers for Graves' disease (GD).
• Accurate quantification of TSI is essential for diagnosing and managing autoimmune thyroid disorders.
• Existing diagnostic methods may have limitations in sensitivity or specificity.

Purpose of the Study:

• To develop and validate a novel, sensitive, and specific bioassay for quantifying TSI.
• To assess the diagnostic performance of the new bioassay in patients with various thyroid and autoimmune diseases.
• To compare the novel bioassay with existing anti-TSHR binding assays.

Main Methods:

• Engineered a cell line (MC4-CHO-Luc) expressing a chimeric TSH receptor and a cAMP-dependent luciferase reporter gene.
• Quantified TSI using specimen-to-reference ratio (SRR%) in 271 patients and 180 controls.
• Evaluated assay sensitivity, specificity, precision, and interference using receiver operating characteristic analysis and interference testing.

Main Results:

• Achieved 96% sensitivity and 99% specificity for untreated Graves' disease (AUC 0.989).
• Demonstrated high precision with coefficients of variation ranging from 11.5% to 15.7%.
• TSI levels were significantly higher in GD patients (untreated or treated) compared to controls and other thyroid conditions (P < 0.0001).

Conclusions:

• The novel TSI-Mc4 bioassay accurately measures functional TSI, a biomarker for Graves' disease.
• The bioassay exhibits high diagnostic accuracy and robustness, with no significant interference.
• This standardized bioassay has the potential to substantially improve the diagnosis of autoimmune diseases involving TSHR autoantibodies.