Sensitivity of three thyrotropin receptor antibody assays in thyroid-associated orbitopathy

• Published in: Journal of medical biochemistry Vol. 41; no. 2; pp. 211 - 220
• Main Authors: Sarić-Matutinović, Marija, Diana, Tanja, Nedeljković-Beleslin, Biljana, Ćirić, Jasmina, Žarković, Miloš, Perović-Blagojević, Iva, Kahaly, George J, Ignjatović, Svetlana
• Format: Journal Article
• Language: English
• Published: Serbia Society of Medical Biochemists of Serbia, Belgrade 08.04.2022
• Subjects: bioassay; bridge binding assay; eclia binding assay; Original Paper; thyroid-associated orbitopathy; thyrotropin receptor antibodies; bioassay; ECLIA binding assay; bridge binding assay; thyroid-associated orbitopathy; thyrotropin receptor antibodies
• ISSN: 1452-8258; 1452-8266
• DOI: 10.5937/jomb0-34718

Thyrotropin receptor autoantibodies (TSH-RAb) are indispensable biomarkers in the laboratory assessment of thyroid-associated orbitopathy (TAO). Clinical sensitivity of three different assays for TSH-R-Ab determination was evaluated in patients with TAO. 87 consecutive TAO patients were enrolled and their serum samples analyzed in parallel with three assays. An ECLIA competitive binding and a chemiluminescent bridge immunoassay were used to measure total and binding TSH-R-Ab concentration, while their functional activity was determined using a stimulatory TSH-R-Ab (TSAb) cellbased bioassay. Compared to the two binding assays (ECLIA p<0.001, bridge p=0.003), the TSAb bioassay was more sensitive pertaining to the positive detection of TSH-R-Ab in TAO patients. No difference (p=0.057) was noted between the ECLIA and bridge assays regarding sensitivity rate. All patients with active and/or moderate-to-severe TAO tested positive in the TSAb bioassay (100% and 100%, respectively), while the positivity rates for bridge and ECLIA binding assays were 89.7% and 82.1% for active TAO, and 90.2% and 86.3% for severe TAO, respectively. Negative predictive values of the bioassay, bridge, and ECLIA assays were 100%, 75%, and 71%, respectively for active TAO, and 100%, 86%, and 71%, respectively for moderate-to-severe TAO. The superiority of the bioassay was most prominent in euthyroid (ET) TAO. Positivity rates of the TSAb bioassay, bridge and ECLIA binding assays were 89.6%, 75%, and 64.6%, respectively for inactive TAO; 86.1%, 69.4%, and 52.8%, respectively for mild TAO; 87.5%, 62.5%, and 12.5%, respectively for euthyroid TAO. The bridge assay correlated better with the ECLIA binding assay (r=0.893, p<0.001), compared to the bioassay (r=0.669, p<0.001). In patients with TAO of various activity and severity, the TSAb bioassay demonstrates a superior clinical performance compared to both ECLIA and bridge binding assays.