1. Novel chimeric thyroid-stimulating hormone-receptor bioassay for thyroid-stimulating immunoglobulins
- Author
-
George J. Kahaly, Y. Li, Leonard D. Kohn, S. D. Lytton, and P. D. Olivo
- Subjects
Thyroid nodules ,endocrine system ,medicine.medical_specialty ,Translational Studies ,Recombinant Fusion Proteins ,Immunology ,CHO Cells ,Biology ,Protein Engineering ,Sensitivity and Specificity ,Thyroiditis ,Cricetulus ,Cricetinae ,Internal medicine ,medicine ,Animals ,Humans ,Immunology and Allergy ,Bioassay ,Transgenes ,Thyroid ,Area under the curve ,Autoantibody ,Reproducibility of Results ,Receptors, Thyrotropin ,medicine.disease ,Graves Disease ,Endocrinology ,medicine.anatomical_structure ,Thyroid Stimulating Immunoglobulin ,Biological Assay ,Immunoglobulins, Thyroid-Stimulating ,Protein Binding ,Hormone - Abstract
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 < 0·0001) compared with TSI levels of patients with Hashimoto's thyroiditis (51 ± 37), autoimmune diseases without GD (24 ± 10), thyroid nodules (30 ± 26) and controls (35 ± 18). The bioassay showed greater sensitivity when compared with anti-TSHR binding assays. In conclusion, the TSI-Mc4 bioassay measures the functional biomarker accurately in GD with a standardized protocol and could improve substantially the diagnosis of autoimmune diseases involving TSHR autoantibodies.
- Published
- 2010