Novel chimeric thyroid-stimulating hormone-receptor bioassay for thyroid-stimulating immunoglobulins.
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.
Department of Medicine I, Gutenberg University Medical Center, Mainz, Germany.
S D
SD
Lytton
Y
Y
Li
P D
PD
Olivo
L D
LD
Kohn
G J
GJ
Kahaly
D000818:Animals; D001681:Biological Assay; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006111:Graves Disease / Q000097:blood / Q000175:diagnosis* / Q000276:immunology / Q000503:physiopathology; D006801:Humans; D018828:Immunoglobulins, Thyroid-Stimulating / Q000097:blood; D011485:Protein Binding / Q000235:genetics; D015202:Protein Engineering; D011989:Receptors, Thyrotropin / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D019076:Transgenes / Q000235:genetics
D018828:Immunoglobulins, Thyroid-Stimulating; D011989:Receptors, Thyrotropin; D011993:Recombinant Fusion Proteins