Increased sensitivity of a new assay for anti-thyroglobulin antibody detection in patients with autoimmune thyroid disease

Clinical implications of changing thyroglobulin and antithyroglobulin antibodies analytical methods in the follow-up of patients with differentiated thyroid carcinoma

BACKGROUND AND AIMS

Patients' response to treatment in differentiated thyroid cancer (DTC) is classified according to serum thyroglobulin concentrations (Tg), usually using the American Thyroid Association guidelines and considering potential interfering anti-thyroglobulin antibodies (Ab-Tg). We aim to evaluate the clinical implications of changing Tg and Ab-Tg quantification method.

MATERIAL AND METHODS

Tg and Ab-Tg were quantified in 82 serum samples (60 from DTC patients) by Elecsys and Access immunoassays.

RESULTS

Elecsys immunoassay rendered higher values of Tg than Access: mean bias 5.03 ng/mL (95%CI:-14.14-24.21). In DTC patients, there was an almost perfect agreement for response classification (kappa index = 0.833). Discrepancies appeared in patients with undetermined response, with a more tendency to subclassification with Access. Ab-Tg showed a poor correlation (r = 0.5394). When Elecsys cut-off was reduced to 43 IU/mL, agreement for positive/negative classification improved from a kappa index of 0.607 to 0.650. Prospective study with personalized follow-up showed that only 6.3% of Tg results required an analytical confirmation, being confirmed 93% of them.

CONCLUSIONS

Despite the biases observed, clinical impact of an analytical change is minimal in patients' management. However, cautious and personalized follow-up period after the change is still mandatory, especially in patients with Tg levels between 0.2 and 1 ng/mL.

The Association Between Chronic Lymphocytic Thyroiditis and the Progress of Papillary Thyroid Cancer

BACKGROUND

Whether chronic lymphocytic thyroiditis (CLT) influences the risk of development and the progression of papillary thyroid cancer (PTC) remains uncertain. We investigated the effects of CLT on the clinicopathologic features and prognosis of PTC.

METHODS

Two thousand nine hundred twenty-eight consecutive patients with PTC treated between 2009 and 2017 were divided into two groups: one with chronic lymphocytic thyroiditis and one without; 1174 (40%) of the patients had coincident CLT.

RESULTS

In univariate analysis, CLT correlated positively with small tumor size, frequent extrathyroidal extension, multifocal diseases, and p53 but negatively with central lymph node (LN) metastasis and BRAF mutation. In multivariate analysis, CLT was associated with extrathyroidal extension and multifocal disease; however, it was not a prognostic factor for recurrence even though it was associated with two aggressive factors. Compared with patients with PTC alone, there were more retrieved central LNs in the PTC + CLT group, and these patients also underwent more invasive diagnostic tests such as fine needle aspiration cytology and frozen biopsy of LN.

CONCLUSIONS

The CLT patients with PTC had better behavior features and prognoses than did those with PTC alone despite frequent multifocality and extrathyroidal extension. However, precaution may be necessary to avoid performing invasive diagnostic procedures for lateral LN metastasis and to manage the patients appropriately.

Data on characterization of glass biochips and validation of the label-free biosensor for detection of autoantibodies in human serum

The data represent in-depth characterization of a novel method for highly sensitive simultaneous measuring in human serum of both critical parameters of autoantibodies: concentration and native kinetics. The latter refers to autoantibody interaction with free, not immobilized, antigen. The method and related biosensors are based on the spectral-correlation and spectral-phase interferometry. The data cover: multi-factor optimization and quantitative characterization of the developed affordable single-used biochips, including X-ray photoelectron spectroscopy (XPS) control of chemical modifications of the surface during fabrication; antibody screening; optimization and verification of protocols for label-free biosensing in human serum; mathematical model for fitting experimental data and calculation of kinetic constants of interaction of autoantibodies with free antigen; comprehensive verification of the method specificity; correlation between the data obtained with the developed biosensor and with enzyme linked immunosorbent assay (ELISA); comparison of analytical characteristics of the developed biosensor with the most advanced label-based methods. The data importance is confirmed by a companion paper (DOI 10.1016/j.bios.2020.112187), which shows that the combination of mentioned autoantibody parameters is promising for more accurate criteria for early diagnostics and efficient therapy of autoimmune disorders. The obtained data can be used in development of a wide range of biosensors, both label-free and based on various labels.

Definition of the upper reference limit for thyroglobulin antibodies according to the National Academy of Clinical Biochemistry guidelines: comparison of eleven different automated methods

Purpose

In the last two decades, thyroglobulin autoantibodies (TgAb) measurement has progressively switched from marker of thyroid autoimmunity to test associated with thyroglobulin (Tg) to verify the presence or absence of TgAb interference in the follow-up of patients with differentiated thyroid cancer. Of note, TgAb measurement is cumbersome: despite standardization against the International Reference Preparation MRC 65/93, several studies demonstrated high inter-method variability and wide variation in limits of detection and in reference intervals. Taking into account the above considerations, the main aim of the present study was the determination of TgAb upper reference limit (URL), according to the National Academy of Clinical Biochemistry guidelines, through the comparison of eleven commercial automated immunoassay platforms.

Methods

The sera of 120 healthy males, selected from a population survey in the province of Verona, Italy, were tested for TgAb concentration using eleven IMA applied on as many automated analyzers: AIA-2000 (AIA) and AIA-CL2400 (CL2), Tosoh Bioscience; Architect (ARC), Abbott Diagnostics; Advia Centaur XP (CEN) and Immulite 2000 XPi (IMM), Siemens Healthineers; Cobas 6000 (COB), Roche Diagnostics; Kryptor (KRY), Thermo Fisher Scientific BRAHMS, Liaison XL (LIA), Diasorin; Lumipulse G (LUM), Fujirebio; Maglumi 2000 Plus (MAG), Snibe and Phadia 250 (PHA), Phadia AB, Thermo Fisher Scientific. All assays were performed according to manufacturers’ instructions in six different laboratories in Friuli-Venezia Giulia and Veneto regions of Italy [Lab 1 (AIA), Lab 2 (CL2), Lab 3 (ARC, COB and LUM), Lab 4 (CEN, IMM, KRY and MAG), Lab 5 (LIA) and Lab 6 (PHA)]. Since TgAb values were not normally distributed, the experimental URL (e-URL) was established at 97.5 percentile according to the non-parametric method.

Results

TgAb e-URLs showed a significant inter-method variability. Considering the same method, e-URL was much lower than that suggested by manufacturers (m-URL), except for ARC and MAG. Correlation and linear regression were unsatisfactory. Consequently, the agreement between methods was poor, with significant bias in Bland–Altman plot.

Conclusions

Despite the efforts for harmonization, TgAb methods cannot be used interchangeably. Therefore, additional effort is required to improve analytical performance taking into consideration approved protocols and guidelines. Moreover, TgAb URL should be used with caution in the management of differentiated thyroid carcinoma patients since the presence and/or the degree of TgAb interference in Tg measurement has not yet been well defined.

In-House Solid-Phase Radioassay for the Detection of Anti-thyroglobulin Autoantibodies in Patients with Differentiated Thyroid Cancer

Thyroglobulin autoantibodies (TgAb) are estimated to detect potential interferences in thyroglobulin (Tg) immunoassays and also for the diagnosis of autoimmune thyroid disease. A user friendly and robust in-house solid-phase radioassay was standardized and parameters like sensitivity, reproducibility and stability were assessed. Further, it was validated and evaluated for the detection of autoantibodies in differentiated thyroid cancer (DTC) patients. Totally 301 samples received in our laboratory for routine serum Tg estimation were studied. The samples were analyzed for TgAb by the solid-phase radioassay developed in-house and compared with commercial anti-hTg IRMA kit (Immunotech, France). The control group comprised of 37 euthyroid males from our Centre. The intra- and inter-assay CVs for the two quality control samples (Control A = 104 ± 12.6 IU/mL and Control B = 1029 ± 114 IU/mL) were found less than or equal to 6.05 and 13.85 % respectively. Solid-phase radioassay showed a good agreement on comparison with Immunotech IRMA (r = 0.99). Using the proposed cut-off thresholds (in-house solid-phase radioassay 52 IU/mL and Immunotech IRMA 30 IU/mL), 5.4 % of the control subjects were positive for TgAb by both the methods. Prevalence of TgAb in DTC patients was 17.3 and 16.6 % using the Immunotech kit and in-house solid-phase radioassay respectively. The in-house solid-phase radioassay has the requisite sensitivity for the evaluation of TgAb comparable to commercial kit and also suitable for routine use as it is rapid, user friendly and economical.

Implications of thyroglobulin antibody positivity in patients with differentiated thyroid cancer: a clinical position statement

BACKGROUND

Even though the presence of antithyroglobulin antibodies (TgAbs) represents a significant problem in the follow-up of patients with differentiated thyroid cancer (DTC), the current guidelines on the management of DTC that have been published in recent years contain no text concerning the methods to be used for detecting such antibody-related interference in thyroglobulin (Tg) measurement or how to manage TgAb-positive patients in whom Tg cannot be used reliably as a tumor marker.

AIM

An international group of experts from the European Thyroid Association Cancer Research Network who are involved in the care of DTC patients met twice to form a consensus opinion on how to proceed with treatment and follow-up in TgAb-positive DTC patients based on the available evidence in the literature. Here we will report on the consensus opinions that were reached regarding technical and clinical issues.

RESULTS

This clinical opinion article provides an overview of the available evidence and the resulting consensus recommendations. The current literature does not provide sufficient data for giving evidence-based answers to many questions arising in the care of TgAb-positive DTC patients. Where insufficient evidence was available, a thorough discussion by a group of physician-scientists, all of whom have a distinguished track record in thyroid cancer care, was held to arrive at a consensus expert opinion. The questions and answers discussed were then summarized into an algorithm for the management of TgAb-positive patients.

CONCLUSION

We were able to define 26 consensus expert recommendations and a resulting algorithm for the care of TgAb-positive DTC patients.

Thyroglobulin autoantibodies in patients with papillary thyroid carcinoma: comparison of different assays and evaluation of causes of discrepancies

CONTEXT

Thyroglobulin autoantibodies (TgAb) have been proposed as a surrogate marker of thyroglobulin in the follow-up of differentiated thyroid carcinoma. Commercially available TgAb assays are often discordant. We investigated the causes of discrepancy.

DESIGN

TgAb were measured by three noncompetitive immunometric assays and three competitive RIA in 72 patients with papillary thyroid carcinoma and associated lymphocytic thyroiditis (PTC-T), 105 with papillary thyroid carcinoma and no lymphocytic thyroiditis (PTC), 160 with Hashimoto's thyroiditis, and in 150 normal subjects. The results of the six assays were correlated. TgAb epitope pattern, evaluated by inhibition of serum TgAb binding to thyroglobulin by TgAb-Fab regions A, B, C, and D, were compared in sera which were positive in all six assays (concordant sera) and positive in only one to five assays (discordant sera) were compared. TgAb International Reference Preparation (IRP) was measured in 2007 and 2009.

RESULTS

The correlations of the six assays ranged from -0.01 to 0.93 and were higher in PTC-T and Hashimoto's thyroiditis than in PTC and normal subjects. Two uncorrelated components, one including the three immunometric assays, the other the three RIA, explained 40 and 37% of the total variance of the results of the six assays. The levels of inhibition were higher in concordant sera than in discordant sera by TgAb-Fab region B (27.0%, 21.2-34.0 vs. 6.0%, and 2.7-12.7%) and region C (30.5%, 21.3-37.7 vs. 4.0%, and 1.0-6.5%); thus, the epitope pattern was more homogeneous in concordant sera than in discordant sera. TgAb IRP ranged from 157 to 1088 (expected 1000) IU/ml in 2009; results in 2007 were similar in all but two assays.

CONCLUSIONS

TgAb assays are highly discordant. Discrepancy is lower when comparing assays with similar methodology. Results of TgAb from PTC-T are more concordant than those from PTC because their epitope pattern is more restricted. The internal standardization of TgAb is generally, but not completely, satisfactory.

Measuring Thyroglobulin Concentrations in Patients with Differentiated Thyroid Carcinoma

Thyroid carcinomas are the most common malignant endocrine tumors. Thyroglobulin (Tg), a specific thyroid protein, is the most important tumor marker in thyroid oncology. After total thyroidectomy or radioiodine therapy, detectable or increasing serum Tg levels in patients with differentiated thyroid carcinoma indicate persistence of active thyroid tissue or cancer recurrence. Serum Tg concentration primarily reflects three variables: the mass of differentiated thyroid tissue present; the degree of thyrotropin receptor stimulation and the intrinsic ability of the tumor to synthesize and secrete Tg. Measurement of serum Tg by current immunometric (IMA) and radioimmunological (RIA) assays encounters some methodological problems which can diminish its clinical importance. Discrepancy between the results for Tg using different methods may be caused by: different reference materials, specific properties of the primary and secondary antibodies for antigenic determinants on Tg and diverse binding affinities of these epitopes, together with interference by serum factors (usually antibodies to Tg (TgAb)) with the primary and secondary Tg antibodies from the diagnostic set. In the presence of endogenous TgAb, Tg values measured by immunoradiometric assay (IRMA) and similar assays are usually lower than the real concentrations, while in RIA apparently lower or higher results can be obtained. Falsely low values may lead to delay in necessary treatment, while an inappropriately high Tg value can cause patient anxiety and unnecessary scans. Despite current methodological limitations, serum Tg measurement is a useful test for determining worsening disease and monitoring the effects of therapy in patients who have undergone surgery for differentiated thyroid carcinoma.

'Linkage analysis of thyroid antibody production: evidence for shared susceptibility to clinical autoimmune thyroid disease

CONTEXT

Epidemiological data suggest a genetic susceptibility to thyroid antibody (TAb) production.

OBJECTIVE

The objective of the study was to identify genetic loci that are linked with TAb production.

DESIGN

The design of the study was a whole genome linkage study in families with clustering of thyroid autoimmunity.

SETTINGS

The study took place at an academic medical center.

PARTICIPANTS

Participants included 102 multigenerational families (540 individuals) multiplex for autoimmune thyroid disease (AITD) and TAb production.

MAIN OUTCOME MEASURES

We computed two-point logarithm of odds (LOD) scores and multipoint heterogeneity LOD scores for 400 microsatellite markers spanning the entire human genome at an average distance of 10 cm (approximately 10 Mb).

RESULTS

Three loci showed evidence for linkage with TAb production: 1) 2q locus, which gave a maximum multipoint heterogeneity LOD score (HLOD) of 2.8 and contained the CTLA-4 gene, previously reported to be linked and associated with clinical AITD; (2) 6p locus (HLOD 2.5), which was the same AITD-1 locus found to be linked with clinical AITD; and (3) 8q locus (HLOD 2.2), which contained the thyroglobulin gene, also previously reported to be linked and associated with AITD. All loci that were linked to TAb were also linked to AITD, suggesting that TAb and AITD share the same genetic predisposition.

CONCLUSIONS

We conclude that: 1) some of the genes/loci predisposing to TAb and AITD are shared, whereas distinct genes/loci also exist; (2) the presence of TAb in relatives of AITD patients may be associated with increased risk for the development of clinical AITD; and (3) further studies are needed to determine the predictive value of TAb levels for the development of clinical AITD in relatives of patients with familial AITD.

Performance characteristics of 5 automated thyroglobulin autoantibody and thyroid peroxidase autoantibody assays

BACKGROUND

Measurement of thyroid peroxidase autoantibodies (TPOAb) is useful in diagnosing patients with autoimmune thyroid disease. Measurement of thyroglobulin autoantibodies (TgAb) is used to detect potential interferences with thyroglobulin immunoassays and in limited situations for the diagnosis of autoimmune thyroid disease.

METHODS

The limit of detection, imprecision, reference interval, method comparison and diagnostic concordance for the ADVIA Centaur, ARCHITECT i2000, AxSYM, Immulite 2000, Modular E170 (TPOAb only), and UniCel DxI 800 (TgAb only) methods were evaluated. The Advantage was used as the comparison method.

RESULTS

Total imprecision ranged from 2.6% to 14.9% for TgAb and 2.1% to 15.8% for TPOAb. Passing-Bablok slopes ranged from 0.51 to 10.4 (TgAb) and 1.05 to 7.12 (TPOAb) with correlation coefficients of 0.48 to 0.82 (TgAb) and 0.66 to 0.78 (TPOAb). Assay cutoffs were adjusted using a common set of reference interval samples. Concordance with the Advantage assay using the new cutoffs was found to be improved and ranged from 68.5% to 84.7% (TgAb) and 77.5% to 84.7% (TPOAb).

CONCLUSIONS

Although all assays generally performed well, assay concordance for a negative or positive result ranged from 54.2 to 84.7%. Quantitative agreement between methods was generally poor and methods could not be used interchangeably. Additional standardization efforts are required to improve inter-method agreement.

Electrogenerated Chemiluminescence in Polyelectrolyte Multilayers: Efficiency and Mechanism

The presence of an ultrathin film of polyelectrolyte complex, formed by the multilayering method, on an electrode was shown to enhance the intensity of electrogenerated chemiluminescence (ECL) from the tris(2,2')bipyridylruthenium(II)/tripropylamine system. Platinum electrodes coated with up to 17 layers of poly(diallyldimethylammonium chloride) or poly(vinylmethylpyridine), alternately layered with poly(styrenesulfonate), revealed significant differences in enhancement of ECL, depending on the identity of the multilayer. ECL following deposition of each layer showed an oscillating intensity of light emission, which alludes to the importance of surface and bulk charge. This effect, along with others, such as increased output with increasing tripropylamine concentration, was used to suggest a mechanism for enhanced ECL intensity at multilayer-coated electrodes.

Clinical evaluation of a microsphere bead-based flow cytometry assay for the simultaneous determination of anti-thyroid peroxidase and anti-thyroglobulin antibodies

OBJECTIVES

Multiplexing technologies based on the use of microspheres as the solid phase have opened new possibilities for the analysis of autoantibodies. As an alternative to the traditional immunoassays, it is possible to use these methods in combination with flow cytometry for simultaneous measurement of anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies.

DESIGN AND METHODS

We studied 127 serum samples sent to our laboratory for the quantitation of anti-TPO and anti-Tg antibodies. Clinical information was available for all of the patients studied. The samples were analyzed simultaneously for both antibodies by flow cytometry (FIDIS, BMD, France), and individually for each of the antibodies by an automated enzyme immunoassay (UniCap, Pharmacia Diagnostics, Germany).

RESULTS

A significant association between the results was observed. The kappa agreement indices between the methods were 0.859 and 0.832 for anti-TPO and anti-Tg, respectively. Discrepant results between the two techniques were observed with no common cause. Anti-TPO and anti-Tg antibodies exhibited a non-Gaussian distribution. The areas under the ROC curves were similar for both methods used; for anti-TPO, 0.884 (Pharmacia) and 0.853 (BMD), and for anti-Tg, 0.833 (Pharmacia) and 0.837 (BMD).

CONCLUSION

Cytometry multiplex technology offers a true alternative to conventional immunoassays in the analysis of anti-TPO and anti-Tg antibodies.

Insight into Graves' hyperthyroidism from animal models

Graves' hyperthyroidism can be induced in mice or hamsters by novel approaches, namely injecting cells expressing the TSH receptor (TSHR) or vaccination with TSHR-DNA in plasmid or adenoviral vectors. These models provide unique insight into several aspects of Graves' disease: 1) manipulating immunity toward Th1 or Th2 cytokines enhances or suppresses hyperthyroidism in different models, perhaps reflecting human disease heterogeneity; 2) the role of TSHR cleavage and A subunit shedding in immunity leading to thyroid-stimulating antibodies (TSAbs); and 3) epitope spreading away from TSAbs and toward TSH-blocking antibodies in association with increased TSHR antibody titers (as in rare hypothyroid patients). Major developments from the models include the isolation of high-affinity monoclonal TSAbs and analysis of antigen presentation, T cells, and immune tolerance to the TSHR. Studies of inbred mouse strains emphasize the contribution of non-MHC vs. MHC genes, as in humans, supporting the relevance of the models to human disease. Moreover, other findings suggest that the development of Graves' disease is affected by environmental factors, including infectious pathogens, regardless of modifications in the Th1/Th2 balance. Finally, developing immunospecific forms of therapy for Graves' disease will require painstaking dissection of immune recognition and responses to the TSHR.