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

• Published in: Clinical and experimental immunology 2010-12, Vol.162 (3), p.438-446
• Main Authors: Lytton, S. D., Li, Y., Olivo, P. D., Kohn, L. D., Kahaly, G. J.
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Animals; Autoantibodies; Autoimmune diseases; Bilirubin; Biological and medical sciences; Biological Assay; biomarker; biomarkers; cell‐based assay; chimeric TSH receptor; CHO Cells; Cricetinae; Cricetulus; Cyclic AMP; Data processing; Fundamental and applied biological sciences. Psychology; Graves Disease - blood; Graves Disease - diagnosis; Graves Disease - immunology; Graves Disease - physiopathology; Graves' disease; Hashimoto's thyroiditis; Hemoglobin; Hormones; Humans; Immunoglobulins; Immunoglobulins, Thyroid-Stimulating - blood; Lipids; luciferase reporter; Nodules; Protein Binding - genetics; Protein Engineering; Receptors, Thyrotropin - genetics; Receptors, Thyrotropin - metabolism; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Reporter gene; Reproducibility of Results; Sensitivity and Specificity; Standard deviation; thyroid diseases; Thyroid-stimulating hormone; thyroid-stimulating hormone receptors; thyroid‐stimulating immunoglobulins; Transgenes - genetics; Translational Studies
• ISSN: 0009-9104; 1365-2249
• DOI: 10.1111/j.1365-2249.2010.04266.x

Summary Thyroid‐stimulating immunoglobulins (TSI) are a functional biomarker of Graves' disease (GD). To develop a novel TSI bioassay, a cell line (MC4‐CHO‐Luc) was bio‐engineered to constitutively express a chimeric TSH receptor (TSHR) and constructed with a cyclic adenosine monophosphate (cAMP)‐dependent luciferase reporter gene that enables TSI quantification. Data presented as percentage of specimen‐to‐reference ratio (SRR%) were obtained from 271 patients with various autoimmune and thyroid diseases and 180 controls. Sensitivity of 96% and specificity of 99% for untreated GD were attained by receiver operating characteristic analysis, area under the curve 0·989, 95% confidence interval 0·969–0·999, P = 0·0001. Precision testing of manufactured reagents of high, medium, low and negative SRR% gave a percentage of coefficient‐of‐variation of 11·5%, 12·8%, 14·5% and 15·7%, respectively. There was no observed interference by haemoglobin, lipids and bilirubin and no non‐specific stimulation by various hormones at and above physiological concentrations. TSI levels from GD patients without (SRR% 406 ± 134, mean ± standard deviation) or under anti‐thyroid treatment (173 ± 147) were higher (P