TSH Receptor Antibody Measurement Research Articles

Brief Report - Monoclonal Antibodies Illustrate the Difficulties in Measuring Blocking TSH Receptor Antibodies.

TSH receptor (TSHR) antibodies are the cause of Graves’ disease and may also be found in patients with Hashimoto’s thyroiditis. They come in at least three varieties: thyroid stimulating, thyroid blocking and neutral. The measurement of TSH receptor antibodies in Graves’ disease and Hashimoto’s thyroiditis is a common clinical activity and can be useful in diagnosis and prognosis. We show that it is not possible to detect the blocking variety of TSHR antibody in patients with Graves’ disease because the stimulating antibody may overwhelm the measurement of blocking in the bioassays available for their measurement and may blind the valid interpretation of the results. To help explain this in more detail we show a series of studies with monoclonal TSHR antibodies which support this conclusion.

A Higher Cutoff for TSI Would Better Predict Recurrence in Patients With Graves’ Disease?

Introduction: GD is an autoimmune disease mediated by immunoglobulins (Igs) that activate TSH receptor (rTSH). Relapse after withdrawal of antithyroid drugs (ATD) can reach 60%. Measurement of TSH receptor antibodies (TRAb) and thyroid stimulating immunoglobulin (TSI) could be an indirect indicator of GD activity. TRAb assays measures thyroid-stimulating, thyroid-blocking and neutral Igs; TSI assays measures only stimulating Igs. Objetive: Evaluate, prospectively, autoimmunity before and after ATD therapy for thyrotoxicosis through TSI measurement. Methods: Patients were evaluated at the first visit and at the time of ATD withdrawal. TSH, thyroid hormones, TPO antibody, thyroglobulin antibody, and TRAb were measured using eletrochemiluminescent assays Roche Diagnostics; TSI was determined by chemiluminescent assay Siemens Diagnostics. According to manufacturers, TRAb < 1.75 IU/L and TSI < 0.55 IU/L were negative. Results: Sixty-seven patients mean age 45,7±2,45 years, 65 women, were evaluated: 50 at the first visit, 40 (80%) with GD, and 10 (20%) with toxic multinodular goiter (TMNG). TSI diagnostic sensitivity (Sen%) and specificity (Spe%) to diagnose GD were 90% and 100% respectively, similar to that of TRAb, of 89% and 100%. Thirty-six patients were evaluated for recurrence after suspension of ATD (19 of them also had the initial assessment): 21 (58.3%) did not present recurrence in an mean period of 9.5±2.1 months (3-18); and 15 (41.7%) relapsed in 4.4±2.6 months (2-12). In 10/21 patients who did not relapse, and whose TRAb was negative, TSI was positive at low levels, which was responsible for the low Spe% of this test. Assessing possible other cutoff points for the TSI in the recurrence assessment, an adjustment to 1.4 (TSI <1.4 IU/L = negative) raised the Spe% to 86%. Conclusions: In this group, TSI and TRAb were equivalent for GD diagnosis. Many clinical factors have been suggested and TRAb measurement is known to be useful for predicting GD relapse because of the active pathogenic role of TRAb. For predicting recurrence, with the proposed cutoff point proposed by the kit manufacturer for TSI, a better sensitivity was obtained when compared with TRAb (93% versus 67%), despite very low specificity (38%); by raising the cutting point to 1.4 specificity could be increased to 86% without reduced sensitivity. A larger sample in needed to support a higher TSI cutoff point in the clinical routine for the assessment of GD recurrence after ATD.

Predicting the Relapse of Hyperthyroidism in Treated Graves' Disease with Orbitopathy by Serial Measurements of TSH-Receptor Autoantibodies.

The aim of this study was to investigate the potential of the new TSH-receptor antibody (TRAb) assays to predict remission or relapse of hyperthyroidism in patients with Graves' disease (GD) and Graves' orbitopathy (GO). TRAbs were measured retrospectively in sera from a cohort of GD patients with GO (n=117; remission n=38 and relapse n=79-Essen GO biobank) with automated binding immunoassays: TRAb Elecsys (Cobas Roche) and TRAb bridge assay (IMMULITE, Siemens), and the TSAb (thyroid stimulating Ab) cell-based bioassay (Thyretain, Quidel Corp.). To identify relapse risk/remission of hyperthyroidism patients were followed up at least 10 months after the end of antithyroid drug therapy (ATD) therapy. ROC plot analysis was performed to calculate cut-off levels of TRAb and TSAb for prediction of relapse and remission of hyperthyroidism. Cut-off serum levels are provided for timepoints around 3, 6, 10, and 15 months after the beginning of ATD. Repeated measurements of TRAb increase the rate of relapses predictions to 60% (Elecsys), 70% (IMMULITE), and 55% (Thyretain). Patients with remission have consistently TRAb levels below the cut off for relapse in repeated measurements. The cell-based bioassay was the most sensitive - and continued to be positive during follow up [at 15 months: 90% vs. 70% (IMMULITE) and 65% (Elecsys)]. Identification of relapsing hyperthyroidism is possible with automated immunoassays and cell-based bioassay especially with serial TRAb measurements during the course of ATD therapy. Patient who need eye surgery may profit from an early decision towards definitive treatment.

Diagnosis and Management of Graves' Disease in Thailand: A Survey of Current Practice.

Background The data on clinical practice patterns in the evaluation and management of Graves' disease (GD) are limited in Asia. The aims of this survey were to report the current practices in the management of GD in Thailand and to examine any international differences in the management of GD. Methods Members of the Endocrine Society of Thailand who were board certified in endocrinology (N = 392) were invited to participate in an electronic survey on the management of GD using the same index case and questionnaire as in previous North American and European surveys. Results One hundred and twenty responses (30.6%) from members were included. TSH receptor antibody measurement (29.2%), thyroid ultrasound (6.7%), and isotopic studies (5.9%) were used less frequently to confirm the etiology compared with those in North American and European surveys. Treatment with an antithyroid drug (ATD) was the preferred first choice of therapy (90.8%). Methimazole at 10–15 mg/day with a beta-blocker was the initial treatment of choice. The preferred ATD in pregnancy was propylthiouracil in the first trimester and methimazole in the second and third trimesters, which was similar to the North American and European surveys. Conclusion Ultrasound and isotopic studies will be requested only by a small proportion of Thai endocrinologists. Higher physician preference for ATD is similar to Europe, Latin America, and other Asian countries. Geographical differences in the use of ATD, radioactive iodine, and thyroidectomy exist.

SAT-415 Clinical Performance of Thyroid-Stimulating Immunoglobulin for Graves′ Disease Diagnosis

INTRODUCTION The diagnosis of Graves′disease (GD) is likely when patient presents hyperthyroidism, symmetrical goiter and orbitopathy and further evaluation is unnecessary. Nevertheless patient with nodular thyroid or in the absence of clinical orbitopathy, measurement of TSH receptor antibodies (TRAb) is recommended to distinguish GD from toxic multinodular goiter, toxic adenoma and other etiologies. Radioiodine uptake (RAIU) also helps to diagnosis when TRAb is unavailable. Third generation TRAb assays measure all types of TSH receptor antibodies: stimulating, blocking and neutral with an excellent sensitivity and specificity for GD diagnosis. Recently, an automated bioassay for the thyroid stimulating immunoglobulin (TSI) was introduced to improve GD diagnosis. OBJECTIVE To analyze clinical performance of TSI and compare with TRAb assay for GD diagnosis. MATERIAL AND METHODS Serum samples of 117 patients with thyrotoxicosis due to GD, toxic multinodular goiter and toxic adenoma were runned simultaneously in two analytical system commercially available. TRAb was analyzed by Elecsys Anti-TSHR assay (Roche Diagnostics, Germany) in a Cobase411 analyzer (Roche Diagnostics, Germany) and results, according to the manufacturer interval reference, were negative if < 1.75 IU/L (analytical range: 0.3 to 40 IU/L). TSI was measured by Immulite TSI assay (Siemens Healthcare, UK) in Immulite XPi 2000 and results, according to the manufacturer interval reference, were negative if < 0.55 IU/L (analytical range: 0.1 to 40 IU/L). Clinical diagnoses of thyrotoxicosis were determined according to ATA guideline (2016). Statistical analyses were performed using SPSS and MedCalc softwares. Comparison were evaluated by regression equations and were considered significant when p values were < .05. RESULTS From 2017 to 2019 a total of 312 serum samples from 117 patients (96 females) were evaluated with mean age 49.5 ±15.8 years-old (18 to 90 yrs). We excluded 26 results above the analytical measurement range of both assays. A high degree correlation was observed with a slope of 0.647 and an intercept -.094 IU/L. Spearman correlation coefficient was 0.858 (p < 0.0001, 95% CI 0.825 to 0.886). TSI assay had higher sensibility and negative predictive value compared to TRAb (95.6% vs 88.5% and 83.6% vs 54.8%, respectively) but lower specificity and positive predictive value (90.3% vs 100% and 97.5% vs 100%, respectively). The results of TSI assay showed good agreement with those of the TRAb assay (k=0.74). A total of 31 samples were discordant, favoring to TSI assay in all but one case of GD according to clinical diagnosis (TRAb positive and TSI negative). CONCLUSION TSI assay showed an excellent performance for GD diagnosis with a better sensibility than TRAb assay.

Update Graves' disease 2019

Also accordingly to the recent European Thyroid Association Guidelines 2018, TSH receptor antibody (TRAb) measurement is highly sensitive and specific for the detection of Graves' disease (GD) and to distinguish from autoimmune thyroiditis (AIT). Bioassays are used for distinguishing stimulating from blocking antibodies and are used for scientific questions. According to the current guidelines - and with exception for pregnant women - the use of thiamazol/carbimazole is generally favored from propylthiouracil (PTU). In case of relapse or missing remission after 12 up to 18 months antithyroid drug therapy, thyroid ablative therapy including radioiodine therapy or thyroidectomy, respectively, should be performed. TRAb measurement can also be used for outcome prediction. Recently the American Thyroid Association published a new guideline for the management of thyroid disease during pregnancy. According to this, during the first 16 weeks of pregnancy PTU is preferred for the treatment of GD with hyperthyroidism. After the 16th week of pregnancy, there is no clear recommandation which antithyroid drug should be used. The general aim is to reach a maternal serum T4 at the upper serum range or moderately above the reference range with the lowest effective dose of an antithyroid drug. As recently shown, Graves' ophthalmopathy improves significantly following the treatment with the monoclonal antibody teprotumumab which inhibits the IGF 1 receptor. This therapy is, however, not been approved in Germany.

False-positive TSH receptor antibody-a pitfall of third-generation TSH receptor antibody measurements in neonates.

Maternal Graves' disease (GD) during pregnancy may influence thyroid function in fetuses. Neonates born to mothers with high serum TSH receptor antibody (TRAb) levels have been reported to develop 'neonatal GD'. Therefore, evaluations of serum thyroid hormone and TRAb levels in neonates upon birth are crucial for a prompt diagnosis. At delivery, we measured TRAb with third-generation TRAb test using an M22 human monoclonal antibody in neonates by collecting umbilical cord blood in a blood collection tube with lithium-heparin, which provides a whole blood/plasma sample. In recent years, we have encountered positive TRAb levels (more than 2.0 IU/L) in nineteen neonates born to mothers with GD whose thyroid hormone levels were almost within the reference range and serum TRAb levels were less than 10 IU/L. All the neonates with positive TRAb levels did not exhibit thyrotoxicosis. However, when we measured TRAb levels with serum sample in six out of the nineteen cases, their serum TRAb levels were all negative, suggesting a discrepancy of TRAb levels between in lithium-heparin plasma from umbilical cord blood and serum. Moreover, this discrepancy was observed in neonates born to euthyroid mothers, adult active GD patients and healthy volunteers. Since lithium-heparin plasma from umbilical cord blood is widely used in laboratory tests at delivery, we may encounter 'false-positive' TRAb, which may, in turn, lead to a misdiagnosis of neonatal GD. This is a pitfall of third-generation TRAb measurements in neonates, particularly at delivery, and needs to be considered by obstetricians and neonatologists.

TSH-receptor autoantibodies: pathophysiology, assay methods, and clinical applications.

TSH receptor antibodies (TRAbs) are characteristic indicators for the common autoimmune thyroid disease Graves disease (GD). In almost all patients stimulating TRAbs are found leading to hyperthyroidism as these antibodies act in an agonistic manner to TSH. Besides stimulating TRAbs, other TRAbs are also frequently found leading to inhibition of TSH receptor signaling (blocking TRAbs) or to the activation of different signaling cascades resulting in e.g. thyrocyte apoptosis (cleavage antibodies). Patients' sera may contain all three types of TRAbs. Dependent on the activity of these particular TSHR autoantibodies clinical symptoms might change. Within this review we summarize current genetic and environmental factors that are generally accepted for GD's etiology. Binding sides to the TSH receptor as well as the resulting signaling cascades are described just as the current used assay methods for TRAb measurement. Finally, we illustrate the clinical impact of TRAbs in the follow-up of GD patients with special focus on GD patients suffering from Graves' ophthalmopathy.

Comparison of three competitive immunoassays for measurement of TSH receptor antibodies in patients with Graves’ disease

Thyrotropin (TSH) receptor antibodies (TRAb) mediate the hyperthyroidism of Graves’ disease (GD). The aim of the study was to compare the diagnostic performance and assay agreement between three immunoassays for the measurement of TRAb in patients with newly diagnosed GD. TRAb was measured with three different assays [H-TRAb (BRAHMS Diagnostica), M22-Man (RSR Limited) and M22-Aut (Roche Diagnostics)] in 387 participants who were recruited from two Danish population-based studies and diagnosed with GD (n = 101), multinodular toxic goitre (n = 88), primary autoimmune hypothyroidism (n = 100) or included as controls (n = 98). Coefficient of variation for duplicate measurements with each of the three assays were H-TRAb: 3.6%, M22-Man: 9.4%, M22-Aut: 7.7%. Frequency of TRAb positivity in patients with GD were H-TRAb: 95%, M22-Man: 94%, M22-Aut: 96%. Receiver operating characteristic analysis revealed a high sensitivity (H-TRAb: 95%, M22-Man: 93%, M22-Aut: 95%) and specificity (H-TRAb: 99%, M22-Man: 99%, M22-Aut: 97%) for the diagnosis of GD with all assays. Comparison of TRAb levels showed inter-assay variability and values were considerably lower with the M22-Man assay. All TRAb assays showed a high diagnostic performance for GD, but a high inter-assay variability was observed limiting the use of different assays in clinical monitoring of patients with GD.

Measuring TSH receptor antibody to influence treatment choices in Graves' disease.

TSH receptor antibody (TRAb) plays a key role in the pathogenesis of Graves' disease (GD), and its levels correlate with the clinical course. The second- and third-generation TRAb assays have >95% sensitivity and specificity for the diagnosis of GD and have improved the utility of TRAb to predict relapse. TRAb levels decline with antithyroid drug (ATD) therapy and after thyroidectomy. Its level increases for a year following radioactive iodine (RAI) therapy, with a gradual fall thereafter. TRAb level >12IU/l at diagnosis of GD is associated with 60% risk of relapse at 2years and 84% at 4years. The prediction of risk of relapse improves further to >90% with TRAb >7·5IU/l at 12months or >3·85IU/l at cessation of ATD therapy. TRAb tests are not expensive, and hence, TRAb measurements at presentation, after 12months and/or 18months (at cessation) of ATD therapy, could potentially guide treatment choices in GD. Elevated TRAb favours definitive treatment in the form of RAI or thyroidectomy, depending on the presence or absence of moderate-to-severe Graves' ophthalmopathy (GO) and the ability to comply with radiation protection requirements. Use of ATDs in early pregnancy is associated with increased risk of congenital anomalies; early ablative treatment (RAI/surgery) should be considered in women of childbearing age at higher risk of relapse of GD. TRAb ≥5IU/l in pregnant women with current or previously treated GD is associated with increased risk of foetal and neonatal thyrotoxicosis, and hence needs close monitoring. TRAb levels parallel the course of GO, and elevated TRAb is an indication for steroid prophylaxis to prevent progression of GO with RAI therapy.

Pregnancy after definitive treatment for Graves’ disease – Does treatment choice influence outcome?

Women requiring thyroid hormone replacement after definitive therapy (surgery or radioiodine) for Graves' disease who later conceive require an early increase in levothyroxine dose and monitoring of thyroid hormone levels throughout pregnancy. In addition, as TSH receptor antibodies (TRAb) can cross the placenta and affect the fetus, measurement of these antibodies during pregnancy is recommended. To review the management of pregnancies following definitive treatment for Graves' disease in order to assess the rates of maternal hypothyroidism and TRAb measurement. Retrospective chart review of women who had undergone definitive treatment for Graves' disease at a tertiary hospital and subsequently had one or more pregnancies. A total of 29 women were identified, each of whom had at least one pregnancy since receiving definitive treatment for Graves' disease: there were a total of 49 pregnancies (22 in the surgical group and 27 in the radioiodine group). Both groups had high rates of hypothyroidism documented during pregnancy (47 and 50%, respectively). The surgical group was more likely to be euthyroid around the time of conception. Less than half of the women were referred to an endocrinologist or had TRAb measured during pregnancy. Neonatal thyroid function was measured in one-third of live births. One case of neonatal thyrotoxicosis was identified. Adherence to the current American Thyroid Association guidelines is poor. Further education of both patients and clinicians is important to ensure that treatment of women during pregnancy after definitive treatment follows the currently available guidelines.

Management of hyperthyroidism during pregnancy in Asia

Maternal hyperthyroidism in pregnancy is associated with adverse impacts on both mother and fetus. Recently, the American Thyroid Association and the Endocrine Society have published guidelines for the management of thyroid diseases in pregnancy. We aimed to disclose the impact of these guidelines in current practices of Asian members of the Asia-Oceania Thyroid Association (AOTA) regarding the management of hyperthyroidism in pregnancy. Completed questionnaire survey, based on clinical case scenarios, was collected from 321 Asian physician members of AOTA from 21 Asian countries in 2013. For a woman with Graves' disease planning pregnancy, 92% of clinicians favored antithyroid treatment, 52% with propylthiouracil (PTU) while 40% preferred methimazole (MMI). For a pregnant woman with newly diagnosed overt hyperthyroidism, nearly all responders initiated PTU treatment. To monitor dosage of antithyroid drugs, approximately 73% of responders used TSH and free T4 (FT4) levels without free T3 (FT3) (53%) or with FT3 (20%). Majority of responders targeted achieving low serum TSH with FT4 (or total T4) in the upper end of the normal range. For management of gestational thyrotoxicosis, 40% chose to follow up and 52% treated patients with PTU. Although timing of TSH receptor antibodies measurement in pregnant hyperthyroid patients was variable, 53% of responders would check it at least once during pregnancy. Nearly 80% of responders do not treat subclinical hyperthyroidism in pregnancy. Therefore, despite wide variations in the management of hyperthyroidism during pregnancy in Asia, majority of Asian physicians practice within the recommendations of major professional societies.

Relevance of TSH-receptor antibody levels in predicting disease course in Graves’ orbitopathy: comparison of the third-generation TBII assay and Mc4-TSI bioassay

To investigate if TSH-receptor antibody (TRAb) levels measured in early Graves' orbitopathy (GO) stages are predictive of clinical disease course beyond 1 year after initial GO diagnosis and to compare performance of two newly developed TRAb assays (third-generation thyrotropin-binding inhibitor immunoglobulin (TBII) assay vs Mc4-thyroid-stimulating immunoglobulin (TSI) bioassay) in predicting disease course.Newly diagnosed, untreated GO patients whose duration of ocular symptoms was less than 6 months were included. One year after initial diagnosis, all patients were classified as presenting either a mild (Group 1) or severe course (Group 2) according to their clinical manifestations. The measurements of two TRAb assays at initial GO diagnosis were used for analysis.Data from 112 patients were available for analysis. Seventy-three patients (65.2%) were designated as Group 1, and 39 patients (34.8%) as Group 2. Patients with higher initial TRAb levels demonstrated a higher risk of severe disease course upon multiple regression analysis (P<0.01). The cutoff values for the prediction of severe course of the third-generation TBII and Mc4-TSI assays were 10.67 IU/l and 555.10%, respectively, with assay specificities of 84.9 and 89.0%. The TBII assay predictive power (area under the curve (AUC)=0.817; 95% confidence interval (CI) =0.732-0.902) was equivalent to the TSI bioassay (AUC=0.868, 95% CI=0.803-0.934) (P=0.203).The predictive power of the third-generation TBII assay and Mc4-TSI bioassay are similarly strong. Measurement of TRAb using either third-generation TBII or Mc4-TSI in early GO periods would provide important prognostic information on future GO course.

Clinical Utility of TSH Receptor Antibodies

TSH receptor antibodies (TRAb) cause Graves' disease (GD) hyperthyroidism. Widely available TRAb measurement methods have been significantly improved recently. However, the role of TRAb measurement in the differential diagnosis of hyperthyroidism, the prediction of remission of GD hyperthyroidism, the prediction of fetal/neonatal thyrotoxicosis, and the clinical assessment of Graves' ophthalmopathy (GO) are controversial. We reviewed and analyzed the literature reporting primary data on the clinical use of TRAb. We focused our analyses on clinical studies analyzing third-generation TRAb assays. The performance of TRAb in the differential diagnosis of overt hyperthyroidism is excellent, with sensitivity and specificity in the upper 90%. TRAb can accurately predict short-term relapses of hyperthyroidism after a course of antithyroid drugs but are less effective in predicting long-term relapses or remissions. Pregnancies in women with GD with negative TRAb are highly unlikely to result in fetal hyperthyroidism, whereas high titers of TRAb in pregnancy require careful fetal monitoring. GD patients with GO frequently have high TRAb levels. However, there are insufficient data to use the test to predict the clinical course of GO and response to treatment. Third-generation TRAb assays are suitable in the differential diagnosis of hyperthyroidism. In GD, TRAb should be tested before deciding whether methimazole can be stopped. TRAb should be used in pregnant women with GD to assess the risk of fetal thyrotoxicosis. The use of TRAb in GO requires further studies.

Obstetric controversies in thyroidology

It is well known that thyroid disorders commonly affect women. The care of pregnant women affected by thyroid disease is an important clinical challenge for endocrinologists. Hypothyroidism is the commonest problem, and maternal hypothyroxinemia has been linked to adverse feto-maternal outcomes. This article would discuss the controversy regarding first-trimester thyroid hormone deficiency and fetal brain development. Certain obstetric controversies in the management of hyperthyroidism in pregnancy, including the indications of TSH receptor antibody measurements and fetal thyroid status monitoring would also be discussed.

Performance of a third‐generation TSH‐receptor antibody in a UK clinic

UK national guidelines recommend the measurement of TSH receptor antibodies (TRAb) in certain clinical scenarios. A commercial third-generation TRAb autoantibody M22-biotin ELISA assay was introduced in May 2008 in our centre. To evaluate the diagnostic performance of a TRAb assay in a retrospective and subsequently a prospective cohort in a UK centre. A retrospective review of patients with thyroid disease followed by a prospective observational study in consecutive patients with newly found suppressed serum thyrotrophin (TSH). Medical records of 200 consecutive patients with thyroid disorders who had TRAb measured since the introduction of the assay. In a prospective study 44 patients with newly identified hyperthyroidism (TSH < 0·02 mIU/l) had sera assayed for TRAb prior to their clinic appointment at which a final diagnosis was sought. In the retrospective cohort, the manufacturer's cut-off point of TRAb ≥0·4 U/l resulted in a positive predictive value (PPV) of 95%, sensitivity 85%, specificity 94% and negative predictive value (NVP) 79% to diagnose Graves' disease using defined criteria. Receiver operating characteristic (ROC) analysis determined an optimal cut-off point of TRAb ≥3·5 U/l with a 100% specificity to exclude patients without Graves' disease at the cost though of a lower sensitivity (43%). In the prospective study, the sensitivity, PPV, specificity and NPV were all 96% using the ≥0·4 U/l cut-off. When combining hyperthyroid patients from both cohorts the assay sensitivity and specificity at ≥0·4 U/l cut-off were 95% and 92% respectively. A positive TRAb result increased the probability of Graves' disease for a particular patient by 25-35% and only six (2·5%) patients had a diagnosis of hyperthyroidism of uncertain aetiology after TRAb testing. The assay studied specifically identifies patients with Graves' disease. It is a reliable tool in the initial clinical assessment to determine the aetiology of hyperthyroidism and has the potential for cost-savings.

A Novel Bioreporter Assay for Thyrotropin Receptor Antibodies Using a Chimeric Thyrotropin Receptor (Mc4) Is More Useful in Differentiation of Graves' Disease from Painless Thyroiditis Than Conventional Thyrotropin-Stimulating Antibody Assay Using Porcine Thyroid Cells

Graves' disease (GD) is caused by thyrotropin (TSH) receptor antibodies (TSHRAbs) that bind to TSHR and activate thyrocytes. The measurement of TSHRAbs therefore has been used to assist in the diagnosis and management of GD. In this study, we evaluated the clinical significance of a newly developed bioreporter assay for the detection of TSHRAbs (Thyretain). The Thyretain bioreporter assay utilizes a chimeric receptor (Mc4), in which residues 262-335 of TSHR are replaced with a rat lutropin-choriogonadtropin receptor segment. This bioreporter is designed to specifically detect stimulating TSHRAbs (Mc4-TSHRAbs). The Mc4-TSHRAb level of sera obtained from 110 normal healthy controls, 103, 99, and 50 patients with untreated GD, painless Hashimoto's thyroiditis (PT), and subacute thyroiditis (SAT) were 27.3% +/- 11.3%, 327.8% +/- 105.9%, 48.9% +/- 48.5%, and 24.9% +/- 13.4%, respectively. Compared with the Mc4-TSHRAb levels of patients with PT and SAT, and normal healthy controls, the Mc4-TSHRAb levels of untreated GD patients were significantly higher (p < 0.01). The sensitivity and specificity of the Thyretain bioreporter assay for GD and PT were 95.1% and 96.0%, respectively, at the optimal cut-off value of 128%. Measurement of TSHRAbs with a bioassay that uses porcine thyroid cells (TSH-stimulating antibody [TSAb]) showed a positive correlation (r = 0.472, p < 0.001) with the Thyretain assay for untreated GD, and strong positive correlation (r = 0.821, p < 0.001) for the entire untreated GD, PT, and SAT population. The positive rate of Mc4-TSHRAbs for GD was significantly higher than that of TSAb (95.1% vs. 89.3%, p < 0.05) and the negative rate of PT by Mc4-TSHRAbs was also significantly higher than that of TSAb (96.0% vs. 86.9%, p < 0.01). As a result, Mc4-TSHRAbs showed statistically better (p < 0.01) diagnostic accuracy in differentiating GD from PT than TSAb. These data suggest that the Thyretain bioreporter assay with a chimeric TSHR (Mc4) is more useful in the differential diagnosis of GD from PT than the bioassay with wild-type TSHR on porcine thyroid cells.

Intermethod Variability in TSH-Receptor Antibody Measurement: Implication for the Diagnosis of Graves Disease and for the Follow-Up of Graves Ophthalmopathy

We compared the analytical and clinical performance of 3 porcine thyroid receptor antibody (TRAb) methods (1 second- and 2 new third-generation systems) with the conventional TRAb assay based on the human recombinant TSH receptor (hTRAK). We obtained sera from 86 patients with untreated Graves disease (GD) and 71 healthy controls. We measured TRAb concentrations by radioreceptor assay using the hTRAK (Brahms) or the porcine TSH receptor (pRRA) from Beckman-Coulter, by electrochemiluminescence immunoassay (ECLIA) with the Elecsys/Cobas (Roche), and by ELISA using the Medizym TRAb clone (Medipan). Between-run assay imprecision was < or =10% and < or =7.6% for hTRAK and ECLIA, but reached 14% and 14.9% for ELISA and pRRA, respectively. Maximal specificity and sensitivity close to 100% were obtained for hTRAK, ECLIA, and ELISA. pRRA failed to detect positive TRAbs in 5 GD patients. Although calibrated against the same reference standard 90/672, the assays displayed a high intermethod variability. The results were significantly higher by ECLIA and lower by ELISA and pRRA compared with hTRAK. Patients with ophthalmopathy had higher TRAb results by ELISA and pRRA than those without eye disease. Second- and third-generation TRAb assays had similar diagnostic sensitivities in the diagnostic evaluation of GD. Despite the use of the same reference standard for calibration, high intermethod variability in TRAb assay results was seen in untreated GD patients. Assay harmonization is necessary for correct interpretation in the follow-up of Graves ophthalmopathy.

Intermethod Variability in TSH-Receptor Antibody Measurement: Implication for the Diagnosis of Graves Disease and for the Follow-Up of Graves Ophthalmopathy

Intermethod Variability in TSH-Receptor Antibody Measurement: Implication for the Diagnosis of Graves Disease and for the Follow-Up of Graves Ophthalmopathy

Second-generation Thyrotropin Receptor Antibodies Assay and Quantitative Thyroid Scintigraphy in Autoimmune Hyperthyroidism

Graves' disease (GD) is characterized by circulating TSH receptor antibodies (TRAb), and so-called hyperthyroid autoimmune thyroiditis (H-AIT) generally shows negative TRAb results with first-generation assays. However, a positive titer was observed in up to 13% of patients with euthyroid or hypothyroid autoimmune thyroiditis (AIT) by second-generation TRAb assays, and a larger increase is expected in hyperfunctioning forms. A thyroid 99mTc-pertechnetate uptake (TcTUs) cutoff of 2% previously was shown to accurately discriminate between GD and H-AIT. Here we evaluated the relationship between second-generation TRAb assays and TcTUs in 139 patients with untreated autoimmune hyperthyroidism. An increase in TRAb levels was found in 114 of 139 patients (82%). All patients with TcTUs >2% and 66% of those with lower values had positive TRAb measurements. When the cutoff was increased to 5.9 U/l, positive TRAb occurred in 92.6% of those having higher TcTUs and in 1.4% of those with lower TcTUs. TRAb levels significantly increased in patients with TcTUs higher than 2% as compared with those having lower values, while no differences occurred in patients with TcTUs ranging from 0 to 1%, from 1.1 to 1.5%, or from 1.6 to 2%. A significant relationship between TRAb and TcTUs (as well as fT3, fT4, and thyroid volume) was found. TcTUs, fT4, fT3, and thyroid volume significantly increased in patients with positive TRAb (cutoff 1.5 U/l) compared with those testing negative. Our data indicate that a large proportion of patients with hyperthyroidism and hypoechoic thyroid, including those previously diagnosed as having H-AIT, actually have circulating TRAb. TRAb levels predicate the degree of iodine uptake (as measured by TcTUs) and thyroid hyperfunction. The role of baseline TRAb measurement by second-generation assays to predict patients' outcome needs to be further evaluated and compared with TcTUs in prospective studies.