Clinical applications of the 2nd generation assay for anti-TSH receptor antibodies in Graves' disease. Evaluation in patients with negative 1st generation test

Stimulating TSH receptor autoantibodies immunoassay: analytical evaluation and clinical performance in Graves’ disease

Background

Thyroid-stimulating hormone (TSH) receptor (TSHR) autoantibodies (TRAbs) are a heterogeneous group of antibodies (Abs) with different functionalities. Among all TRAbs, only the stimulating ones (S-TRAbs) are considered as the pathogenetic marker of Graves’ disease (GD). To date, the methods available for TRAbs testing are based on immunoassays (IMAs) which detect total serum TRAbs or bioassays which are not suitable in clinical practice, even though they discern Abs functionality. The aim of our work was to evaluate the analytical and clinical performance of a very recent IMA (Immulite TSI method), supposed to test only the serum concentration of S-TRAbs, in comparison with a current method for total TRAbs (Roche/Elecsys IMA).

Methods

We evaluated serum samples of 145 subjects: 46 with untreated (GD), 36 with chronic autoimmune thyroiditis, 3 with atrophic thyroiditis, 10 with multinodular non-toxic goiter and 50 healthy subjects.

Results

The method showed an optimal analytical sensitivity and high precision levels (LoB: 0.04 UI/L, LoD:0.07 UI/L, LoQ:0.14 UI/L, intra-assay CV: 4.2–5.9%, inter-assay: 4.5–7.2%). By receiver operating characteristics curve analysis, we obtained a value of 0.57 (sensitivity: 98.0%, specificity: 99.9%) as the best cut-off to distinguish GD, apart from four cases. Passing Bablok regression and Bland Altman analysis pointed out a good correlation and agreement with Roche method (R2 = 0.98, slope = 1.03, bias = −2.70).

Conclusions

The new method presents very promising analytical characteristics and could be adopted in clinical practice for GD diagnosis. Moreover, the test allows to accurately detect very low values of analyte with a further clinical utility in detecting earlier possible relapses.

There is no elevation of immunoglobulin e levels in Albanian patients with autoimmune thyroid diseases

Background. Studies in several ethnic groups reported high incidence of elevated levels of immunoglobulin E (IgE) in patients with autoimmune thyroid diseases (ATD), especially in patients with Graves' disease. Objective. To study association between serum levels of IgE and thyroid stimulating hormone receptor antibodies (TRAb) in Albanian patients with ATD. Material and Methods. Study was performed in 40 patients with Graves' disease, 15 patients with Hashimoto's thyroiditis, and 14 subjects in the control group. The IgE levels were measured by immunoradiometric assay, whereas the TRAb levels were measured by radioreceptor assay. Results. In all groups of subjects the IgE levels were within reference values (<200 kIU/L). Significant difference in mean concentration of IgE was found between two groups of Graves' disease patients, and those with normal and elevated TRAb levels (22.57 versus 45.03, P < 0.05). Positive correlation was found between TRAb and IgE only in Graves' disease patients (r = 0.43, P = 0.006). Conclusion. In Albanian patients with ATD there is no elevation of IgE levels. This could be the result of low prevalence of allergic diseases in Albanian population determined by genetic and environmental factors.

Association Between Autoantibodies Against Thyroid Stimulating Hormone Receptor and Thyroid Diseases

Aim:

The aim of this study is to determine the relationship between TRAb and different diseases. The highest percentage of increased TRAb levels can be found at patients with Graves’ diseases.

Material and methods:

Study was performed in 70 patients, grouped in three groups, and 14 persons who based on the clinical status and the levels of thyroid hormones do not have any thyroid disease. The TRAb levels has been determined in patients with Graves’ disease (N=40), Hashimoto’s disease (N=15), Plummer’s disease (N=15) and the control group (N=14).

Results:

The highest mean TRAb levels exist in patients with Graves’ disease. There exists a positive correlation between TRAb levels and T3, and T4, while there is no correlation between TSH and TRAb levels in patients with Graves’ disease,. On the other hand, the correlation between TRAb and T3 and T4 in patients with Hashimoto’s diseases and Plummers disease was shown to be positive, but of a low levels.

Clinical value of the first automated TSH receptor autoantibody assay for the diagnosis of Graves' disease (GD): an international multicentre trial

BACKGROUND

Most recently, a new rapid and fully automated electrochemiluminescence immunoassay for the determination of TSH receptor autoantibodies (TRAb) based on the ability of TRAb to inhibit the binding of a human thyroid-stimulating monoclonal antibody (M22) has been established.

OBJECTIVE

To evaluate this assay system in clinical routine based on an international multicentre trial and to compare the results with other established TRAb assays.

PATIENTS AND MEASUREMENTS

Totally 508 Graves' disease (GD), 142 autoimmune thyroiditis, 107 subacute thyroiditis, 109 nonautoimmune nodular goitre, 23 thyroid cancer patients and 446 normal controls were retrospectively evaluated.

RESULTS

ROC plot analysis revealed an area under curve of 0.99 (95% CI: 0.99-1.0) indicating a high assay sensitivity and specificity. The highest sensitivity (99%) and specificity (99%) was seen at a cut-off level of 1.75 IU/l. Here, the calculated positive predictive value was 95%, whereas the negative predictive value was 100%. Applying the ROC plot-derived cut-off of 1.75 IU/l we found a sensitivity for TRAb positivity within the group of newly diagnosed GD patients of 97% which is in accordance to the sum of different nonautomated porcine TSH receptor-based assays with a sensitivity of 94% indicating an excellent analytical performance of the new assay format. Detailed comparison of the automated and the sum of manual assays revealed a near identical specificity.

CONCLUSION

Our results demonstrate that this new assay system has a high sensitivity for detecting GD and specificity for discriminating from other thyroid diseases. This assay may represent the future technology for rapid fully automated TRAb detection.

Reliability of the thyroid stimulating hormone receptor antibodies level determination in diagnosing and prognosing of immunogenic hyperthyroidism

Background/Aim. Graves disease (GD) is defined as hyperthyroidism with diffuse goiter caused by immunogenic disturbances. Antibodies to the thyroid stimulating hormone (TSH) receptors of thyroid gland (TRAb) have crucial pathogenetic importance in the development and maintenance of autoimmune hyperthyroidism. The aim of this study was to identify sensitivity, specificity, positive an negative predictive value of TRAb level in sera of patients with GD as well as to estimate significance of TRAb level for remission and GD relapses occurrence. Methods. We studied prospectively and partly retrospectively 149 patients, 109 female and 40 male patients, 5-78 years old, in the period 1982-2007. There were 96 patients with GD. The control group consisted of 53 patients, 21 with hyperthyroidism of second etiology and 32 patients on amiodarone therapy, with or without thyroid dysfunction TRAb was measured by radioreceptor assay (TRAK Assay and DYNO Test TRAK Human Brahms Diagnostica GMBH). Results. According to the results the sensitivity (Sn) of TRAb test was 80%, specificity (Sp) 100%, positive predictive value (PP) 100% and negative predictive value (NP) 83%. Also, the Sn of hTRAb test was 94%, Sp 100%, PP 100% and NP 94%. Our results show that an increased level of TRAb/hTRAb at the beginning of the disease and the level at the end of medical therapy is associated with an increased number of GD relapses and a shorter remission duration. Conclusion. Detection and measurement of TRAb in serum is a very sensitive method for diagnosing GD and very highly specific in vitro method for differential diagnosis of various forms of hyperthyroidism. Clinical significance of differentiating various forms of hyperthyroidism, using this in vitro assay, lays in adequate therapeutic choice for these entities.

Frequency and characteristics of TBII-seronegative patients in a population with untreated Graves' hyperthyroidism: a prospective study

OBJECTIVE

It is claimed that second generation thyrotropin-binding inhibitory immunoglobulin (TBII) assays have a very high sensitivity for the diagnosis of Graves' hyperthyroidism (GH). However, studies evaluating the accuracy of TBII have been retrospective in nature and/or GH had not been diagnosed independently of TBII. The aim of the present study, therefore, was to prospectively evaluate the frequency and characteristics of TBII-seronegative patients in a population of untreated GH diagnosed independent of serum TBII.

DESIGN

Prospective multicentre observational study.

PATIENTS

A total of 259 consecutive untreated patients with a first episode of GH, diagnosed independent of serum TBII. TBII levels were measured by second generation assay and correlated to thyroid function, clinical characteristics and exposure to environmental factors.

RESULTS

Serum TBII was positive in 245 (94.6%) patients and negative (< 2 IU/l) in 14 (5.4%) patients. TBII-seronegative patients had lower fT4 (median 42.5 vs. 53.9 pmol/l, P = 0.02), T3 (median 3.55 vs. 4.90 nmol/l, P < 0.01) and fT3-index (median 4.30 vs. 6.27, P < 0.01) compared to TBII-seropositive patients. None of the TBII-seronegative patients had TSH-receptor activating mutations, Graves' orbitopathy or pretibial myxedema. Serum TBII was positively correlated to free T3 (fT3)-index and free T4 (fT4)-index (P < 0.01), goitre size (P < 0.01) and the prevalence of Graves' orbitopathy (P < 0.01). There were no significant differences between TBII-seropositive and TBII-seronegative patients in environmental factors.

CONCLUSION

The prevalence of TBII-seronegativity in untreated patients with GH is 5.4% using a second generation assay. TBII-seronegative patients have biochemically less severe thyrotoxicosis and no Graves' orbitopathy. TBII-seronegative and TBII-seropositive patients apparently belong to the same population of GH, albeit the severity of the autoimmune attack is less in TBII-seronegative patients.

Coeliac disease in Dutch patients with Hashimoto’s thyroiditis and vice versa

AIM: To define the association between Hashimoto’s thyroiditis and coeliac disease in Dutch patients.

METHODS: A total of 104 consecutive patients with Hashimoto’s thyroiditis underwent coeliac serological tests (antigliadins, transglutaminase and endomysium antibodies) and HLA-DQ typing. Small intestinal biopsy was performed when any of coeliac serological tests was positive. On the other hand, 184 patients with coeliac disease were subjected to thyroid biochemical (thyroid stimulating hormone and free thyroxine) and thyroid serological tests (thyroglobulin and thyroid peroxidase antibodies).

RESULTS: Of 104 patients with Hashimoto’s thyroiditis, sixteen (15%) were positive for coeliac serology and five patients with documented villous atrophy were diagnosed with coeliac disease (4.8%; 95% CI 0.7-8.9). HLA-DQ2 (and/or -DQ8) was present in all the five and 53 patients with Hashimoto’s thyroiditis (50%; 95% CI 43-62). Of 184 patients with coeliac disease, 39 (21%) were positive for thyroid serology. Based on thyroid biochemistry, the 39 patients were subclassified into euthyroidism in ten (5%; 95% CI 2-9), subclinical hypothyroidism in seven (3.8%; 95% CI 1.8-7.6), and overt hypothyroidism (Hashimoto’s thyroiditis) in 22 (12%; 95% CI 8-16). Moreover, four patients with coeliac disease had Graves’ disease (2%; 95% CI 0.8-5) and one patient had post-partum thyroiditis.

CONCLUSION: The data from a Dutch population confirm the association between Hashimoto’s thyroiditis and coeliac disease. Screening patients with Hashimoto’s thyroiditis for coeliac disease and vice versa is recom-mended.

Serum thyrotropin receptor antibodies concentrations in patients with Graves' disease before, at the end of methimazole treatment, and after drug withdrawal: evidence that the activity of thyrotropin receptor antibody and/or thyroid response modify during the observation period

AIM AND METHODS

We performed a quantitative retrospective analysis of serum thyrotropin receptor antibody (TRAb) concentrations measured by a second-generation radioreceptor assay in 58 patients with Graves' disease (GD) at the onset of the disease, at the end of 18 month methimazole (MMI) treatment, and after MMI withdrawal in order to evaluate the correlation between the presence of these antibodies and the relapse of hyperthyroidism. Sixty healthy subjects were enrolled as a control group.

RESULTS

Before MMI treatment the best cutoff TRAb value for identifying patients with GD was 1.45 UI/L (specificity, 100%; sensitivity, 98.3%). At the end of MMI treatment, serum TRAb concentrations were significantly lower (p < 0.001) than those measured at baseline, but they were still significantly higher (p < 0.001) than those found in the control subjects. At the end of MMI treatment, 44 patients (75.9%) had positive TRAb values (>1.45 UI/L). After MMI withdrawal (median, 15 months), 34 patients (58.6%) became hyperthyroid, 4 patients (6.9%) became hypothyroid, and 20 patients (34.5%) remained euthyroid. There was a significant correlation between serum TRAb concentrations at the end of MMI treatment and the percentage of patients who became hyperthyroid (r: 0.56; p < 0.001) and the time of appearance of hyperthyroidism (r: -0.38; p = 0.03). All 4 patients with TRAb values below 0.9 UI/L at the end of MMI treatment remained euthyroid throughout the follow-up period. Among the 27 patients who had serum TRAb values higher than 4.4 UI/L, 23 developed hyperthyroidism and 4 hypothyroidism. The TRAb values between 0.9 and 4.4 UI/L did not discriminate between the 27 patients (46.6%) who remained euthyroid from those who had relapse of hyperthyroidism. Thus a different TRAb end of treatment cutoff was calculated to identify patients who became again hyperthyroid. This TRAb cutoff value was 3.85 UI/L (sensitivity, 85.3%; specificity, 96.5%). All but 1 patient who had serum TRAb values above 3.85 UI/L became hyperthyroid after MMI was withdrawn (positive predictive value, 96.7%). In these patients, relapse of hyperthyroidism was independent of the changes in serum TRAb concentrations (r: 0.27; p = 0.15) and occurred after a median period of 8 weeks (range, 4-48). Hyperthyroidism also developed in 5 of 24 patients who had serum TRAb concentrations lower than 3.85 UI/L at the end of MMI treatment. In these 5 patients the relapse of hyperthyroidism occurred after a median period of 56 weeks (range, 24-120) and was always accompanied by an increase in serum TRAb concentrations.

CONCLUSIONS

TRAb persist in the blood of most patients with GD after 18 months of MMI treatment. Both the frequency and the time of appearance of hyperthyroidism are closely correlated with serum TRAb concentrations at the end of MMI treatment. Our data would suggest that TRAb maintain stimulating activity after a full course of MMI treatment in the large majority of patients with GD. However, it is likely that the potency of these antibodies and/or the thyroid response to them change during treatment, as suggested by the different values measured in euthyroid control subjects and in euthyroid patients after MMI treatment.

Sensitive thyrotropin and thyrotropin-receptor antibody determinations one month after discontinuation of antithyroid drug treatment as predictors of relapse in Graves' disease

OBJECTIVE

After primary successful antithyroid drug treatment (ATDT), Graves' disease has a relapse rate of 30% to 50%. Previous studies have evaluated age, gender, goiter volume, smoking habits, and the presence of thyrotropin-receptor antibodies (TRAb) as predictive markers to facilitate an individualized patient management. Despite higher sensitivity and specificity of the new second generation human TSH-receptor assay, the predictive value of TRAb for relapse of hyperthyroidism is still controversial. In a recent prospective multicenter study we have previously shown that suppressed or low TSH values predict both early (persistence) and late relapse of Graves' disease. We now present a more detailed analysis of the predictive value of TSH and TRAb for recurrent hyperthyroidism.

METHODS

Four weeks after withdrawal of ATDT, 96 patients were available for thyroid function tests, including a sensitive third-generation TSH assay and a second-generation recombinant TSH receptor assay. Relapse of Graves' disease was evaluated for a total follow-up of 2 years.

RESULTS

Within 2 years, 47 of 96 patients (49%) developed relapse of hyperthyroidism. Nine patients relapsed within the first 4 weeks after withdrawal of ATDT and were thus considered to have persistent Graves' disease. Ten of 15 other patients with TSH levels below 0.3 mU/L without overt hyperthyroidism relapsed within 2 years. Twenty-five of 65 patients with normal TSH (0.3-3.0 mU/L) and 3 of 4 patients with TSH values above 3 mU/L also had recurrent hyperthyroidism. After ATDT cessation, TSH had a positive predictive value of 70% and a negative predictive value of 62% (specificity 85%) for relapse of Graves 'disease. Mean TRAb levels in the group of patients with relapse were significantly higher (11.1 IU/L +/- 0.17) than TRAb values in the remission group (4.5 IU/L +/- 0.6), p < 0.001. Using a cutoff value of 1.5 IU/L, TRAb had low positive and negative predictive values of 49% and 54%, respectively (specificity, 14%), but with a cutoff level of 10 IU/L, predictive values improved to 83% and 62%, respectively (specificity, 92%). Combination of TSH and TRAb determinations did not further improve prediction of relapse. Other factors such as gender, age, goiter volume, smoking habits, presence of thyroid-associated ophthalmopathy, and urinary iodine excretion did not show a significant influence on relapse rate.

CONCLUSION

Low TSH values 4 weeks after ATDT withdrawal predict relapse of Graves' disease, both early (persistence) and, to a lesser extend, within 2 years of follow-up. Also, TRAb above 10 IU/L found in a small subset of patients, correlated with a higher relapse rate.

Evaluation of a coated-tube assay for antithyrotropin receptor antibodies in patients with Graves' disease and other thyroid disorders

The detection of autoantibodies to the thyrotropin-receptor antibody (TRAb) is commonly used in clinical practice for the diagnostic assessment of Graves' disease (GD) and its differential diagnosis from toxic multinodular goiter (MNG) and autonomous adenoma. Additionally, TRAb assays can be useful during antithyroid drug treatment of GD to evaluate the risk of relapse and/or remission. The detection of TRAb was originally performed using a radioreceptor assay based on detergent-solubilized porcine thyroid membranes (TRAb). More recently new assays using purified porcine or recombinant human thyrotropin (TSH) receptor-coated plastic tubes (CT) have been developed (pCT-TRAb or hCT-TRAb). We have evaluated both assays (TRAb and pCTTRAb) in 300 individuals: healthy controls (n = 51); patients with GD before and after treatment (n = 200), patients with MNG (n = 29), and Hashimoto's thyroiditis [HT; n = 20]). All healthy controls and patients with HT had undetectable TRAb using both methods. Patients with active (not treated) GD had higher pCT-TRAb values (mean +/- standard deviation [SD], 58.2% +/- 20.3%, inhibition of TSH binding) compared to TRAb (41.2% +/- 15.4%, p < 0.01, Wilcoxon test). Results (as percent inhibition for both methods) had a positive and significant correlation (r = 0.68, p < 0.001). Moreover TRAb assay had a 97.3% sensitivity and 96.8% specificity; the pCT-TRAb sensitivity was 96.3% and specificity was 98.4% at a cutoff of 1.51 U/L. During treatment of GD, the TRAb method resulted in significantly lower (p < 0.05) values at 12, 24, and 30 months, while pCT-TRAb only exhibited significancy (compared to basal levels) at 30 months. The percent inhibition after 131I treatment of GD was significantly higher for pCT-TRAb (33.7 +/- 25.7) compared to TRAb (21.9 +/- 17.7, p < 0.01, Wilcoxon test). Only one patient with untreated MNG had a positive pCT-TRAb but negative TRAb value. Patients with MNG treated with 131I were divided into two groups: group 1 (only (131)I) or group 2 (hrTSH preceding (131)I). After MNG radioisotopic ablation, five patients had a positive pCT-TRAb and four had a positive TRAb (group 1) while in group 2, three patients had a positive pCT-TRAb and two had a positive TRAb assay. In conclusion, pCT-TRAb usually had higher percent inhibition values compared to TRAb in untreated GD, had a relatively lower decrease in percent inhibition values during treatment but exhibited a slightly increased sensitivity compared to TRAb. An advantage of the pCT-TRAb assay may be because of the coating system itself that might expose more receptor sites for the antibody.

Antithyrotropin receptor antibody: an update

Numerous studies have reported the characteristics and significance concerning antithyrotropin receptor antibodies (TSHR-Abs), which cause Graves' disease and in some cases primary hypothyroidism. However, many unsolved questions concerning those antibodies remain. Here, recent developments in the study of TSHR-Abs are reviewed based on three aspects: mechanisms of TSHR-Ab production, antibody binding epitopes, and clinical TSHR-Ab assays. Mechanisms of TSHR-Ab production are discussed from five points of view: aberrant expression of the major histocompatibility complex, dysregulation of T cells, molecular mimicry, bystander effect, and expansion of autoreactive B cells. Regarding epitopes, unique TSHR-Abs have been reported that may explain the complicated pathophysiology of patients with TSHR-Ab diseases. Finally, recent efforts to improve TSHR-Ab measurements are introduced. Such efforts will contribute to clinical examinations and treatments for thyroid diseases as well as experimental methods of thyroidology.