Second Generation Assay for Thyrotropin Receptor Antibodies Has Superior Diagnostic Sensitivity for Graves’ Disease

Abstract

Detection of autoantibodies to the TSH receptor (TSH-R) in Graves' disease has found widespread use in clinical routine and is performed mostly by commercial RRAs measuring TSH binding inhibitory activity. We report in this study on a second generation TSH binding inhibitory assay using the human recombinant TSH-R with two major improvements: 1) superior diagnostic sensitivity for Graves' disease, and 2) for the first time, nonradioactive and radioactive coated tube (CT) technology. Full-length human recombinant TSH-R was expressed in the K562 leukemia cell line and grown in suspension at a high density. A murine monoclonal antibody was selected for binding to the native TSH-R without interfering with autoantibodies or TSH and was coated to polystyrene tubes. After detergent extraction, TSH-R was affinity immobilized on antibody-coated tubes. The binding of TSH to the TSH-R could be demonstrated by the addition of 125I- or acridinium ester-labeled bovine TSH, and this binding could be inhibited by sera from patients with Graves' disease up to 95%. Subsequently, these novel assays, a CT RRA and a CT luminescence receptor assay, were compared to the conventional RRA based on porcine antigen in a blinded clinical multicenter trial. Sera from 328 patients with Graves' disease (86 untreated, 116 treated, and 126 in remission) and 520 controls (comprised of healthy blood donors and patients with autoimmune diseases or goiter) were tested in all 3 assays. Receiver-operating characteristic plot analysis resulted in a specificity of 99.6% with a sensitivity of 98.8% for both CT assays, compared to 99.6% specificity and 80.2% sensitivity for the conventional RRA (P < 0.001). In all 3 groups of patients with Graves' disease, the 2 CT assays were significantly more sensitive for the disease than the conventional assay, without loss of specificity in the control groups. This increase in sensitivity and the nonradioactive or radioactive CT format constitute a significant improvement over the currently available assays.

Long-term prognosis after medical treatment of Graves' disease in a northern Swedish population 2000–2010

“…Swedish studies from the 1970s and 1980s report somewhat higher relapse rates than our study (7,20) even though definite ablative methods were used more frequently, and that would supposedly lead to fewer and more easily ATD-treated patients at that time. However, TRAb methods are more sensitive today (26), probably affecting the number of patients diagnosed with GD by such assays, as used in 2004 in our study, and may have a better prognosis with ATD. This study reflects the practice in the real world of routine care at district and central hospitals where analysis of TRAb was not part of the clinical decision on if or when to end ATD treatment.…”

Predictive value of maternal second-generation thyroid-binding inhibitory immunoglobulin assay for neonatal autoimmune hyperthyroidism

“…Most related studies have been performed using the first-generation TBII assay and yet second-generation assays are nowadays widely available. Instead of solubilized porcine receptors (14,15), these newer assays use recombinant TSHR coated on a solid-phase surface which provides a markedly improved sensitivity and specificity (16,17,18). To our knowledge, the threshold value indicating a risk for fetal or neonatal autoimmune hyperthyroidism with a second-generation TBII assay has only been investigated in one small study (19).…”

Accuracy of receptor-based methods for detection of thyrotropin-receptor autoantibodies: a new automated third-generation immunoassay shows higher analytical and clinical sensitivity for the differential diagnosis of hyperthyroidism

“…Despite a high specificity (nearly 100%), these assays show a low diagnostic sensitivity, ranging from 52% to 94% (with a mean of 77.5%) in the most relevant literature reports of the last 20 years [10,[12][13][14][15][16][17][18][19][20] (Table 1). As a consequence, a significant proportion (6-48%; mean 22.5%) of GD patients with clinical HT were reported to be TRAb 'negative' by first-generation methods.…”

“…To increase the sensitivity of the TRAb assay, secondgeneration immunoassays that use monoclonal antibodies (mAb), human or porcine TSHR immobilized on a plastic surface and bovine TSH labelled with 125 I, or acridinium ester, or with biotin-streptavidin-peroxidase have become available [15,21]. Several studies have shown that the clinical sensitivity of these assays increases to a mean of 95.9% (range 72.6-100%; Table 1) with a small decrease in specificity (97.9%, range 91.4-100%) [15,[17][18][19][22][23][24][25][26][27][28][29][30].…”