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

Diagnostic, Theranostic and Prognostic Value of Thyroglobulin in Thyroid Cancer

Thyroglobulin (Tg) is an iodinated glycoprotein, which is normally stored in the follicular colloid of the thyroid, being a substrate for thyroid hormone production. Since it is produced by well-differentiated thyroid cells, it is considered a reliable tumor marker for patients with differentiated thyroid carcinoma (DTC) during their follow-up after total thyroidectomy and radioiodine ablation. It is used to monitor residual disease and to detect recurrent disease. After total thyroid ablation, unstimulated highly sensitive Tg measurements are sufficiently accurate to avoid exogenous or endogenous thyrotropin (TSH) stimulation and provide accurate diagnostic and prognostic information in the great majority of DTC patients. Adopting sophisticated statistical analysis, i.e., decision tree models, the use of Tg before radioiodine theranostic administration was demonstrated to be useful in refining conventional, pathology-based risk stratification and providing personalized adjuvant or therapeutic radioiodine administrations. The follow-up of DTC patients aims to promptly identify patients with residual or recurrent disease following primary treatment. Our review paper covers the diagnostic, theranostic and prognostic value of thyroglobulin in DTC patients.

Thyroglobulin and thyroglobulin antibody: an updated clinical and laboratory expert consensus

OBJECTIVE

Thyroglobulin measurement is the cornerstone of modern management of differentiated thyroid cancer, with clinical decisions on treatment and follow-up based on the results of such measurements. However, numerous factors need to be considered regarding measurement with and interpretation of thyroglobulin assay results.

DESIGN

The present document provides an integrated update to the 2013 and 2014 separate clinical position papers of our group on these issues.

METHODS

Issues concerning analytical and clinical aspects of highly-sensitive thyroglobulin measurement will be reviewed and discussed based on an extensive analysis of the available literature.

RESULTS

Thyroglobulin measurement remains a highly complex process with many pitfalls and major sources of interference, especially anti-thyroglobulin antibodies, need to be assessed, considered and, when necessary, dealt with appropriately.

CONCLUSIONS

Our expert consensus group formulated 53 practical, graded recommendations for guidance on highly-sensitive thyroglobulin and TgAb in laboratory and clinical practice, especially valuable where current guidelines do not offer sufficient guidance.

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.

Evaluation of Different Methods for the Detection of Anti- Thyroglobulin Autoantibody: Prevalence of Anti-Thyroglobulin Autoantibody and Anti-Microsomal Autoantibody in Thyroid Cancer Patients

Four anti-thyroglobulin autoantibodies (TgAb) assays were evaluated for their reference interval, method agreement, concordance etc. Prevalence of TgAb and anti-thyroid peroxidase was studied in differentiated thyroid cancer (DTC) and control. Reference intervals for TgAb assays varied from method to method due to varied assay designs. For TgAb correlation coefficients ranged from 0.74 to 0.99 whereas concordance ranged from 81 to 96.1%. Prevalence of thyroid antibodies mainly TgAb was increased in DTC primarily in females. Use of sensitive immunoassays is recommended for thyroid autoantibody measurement. Diagnosis and follow-up are difficult in DTC with coexisting thyroid autoimmunity. Hence, careful monitoring with regular surveillance is suggested.

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.

Serum antithyroglobulin antibody levels are not a good predictive factor on detection of disease activity in patients with papillary thyroid carcinoma

Objective

Thyroglobulin antibodies (TgAb) are detected in thyroid cancer patients up to 25%. We investigated the prognostic value of TgAb positivity in patients with papillary thyroid carcinoma (PTC) after initial therapy.

Patients and Methods

A database of 109 consecutive patients who underwent total thyroidectomy and therapeutic lateral neck dissection followed by remnant ablation for PTC between January 1989 and December 2014 was reviewed We recorded the patients' all serum Tg and TgAb levels over time to establish changing trends. Patients were classified as either positive or negative according to serum TgAb levels. The recurrence or persistence rates in both groups were compared.

Results

Of the 109 patients enrolled 14 patients had TgAb positivity. Thirty-two (29.3%) showed disease recurrence or persistent disease during 101 months of follow-up. Twenty-seven of 95 patients (28.4%) with negative TgAb had persistent or recurrent disease, whereas 5 of 14 patients (35.7%) with positive TgAb had persistence or recurrence (P = 0.57). No significant difference in disease-free survival (115.3 ± 10.8 vs. 224.1 ± 16.6 months, P = 0.78) and overall survival (P = 0.59) was observed between TgAb positive and TgAb negative patients.

Conclusions

TgAb status is not useful as a prognostic and predictive factor for clinical outcomes in patients with PTC in our experience.

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.

Comparison of thyroglobulin and thyroid peroxidase antibodies measured by five different kits in autoimmune thyroid diseases

It is generally believed that the detection of thyroid peroxidase antibodies (TPOAb) is superior to that of thyroglobulin antibodies (TgAb) for the diagnosis of Hashimoto's thyroiditis. However, limited data are available on the comparison of TgAb and TPOAb prevalence as a diagnostic measurement for Hashimoto's thyroiditis using sensitive immunoassays. We herein used five different current immunoassay kits (A-E) to compare the prevalence of TgAb and TPOAb in Hashimoto's thyroiditis (n = 70), Graves' disease (n = 70), painless thyroiditis (n = 50), and healthy control subjects (n = 100). In patients with Hashimoto's thyroiditis, positive TgAb was significantly more frequent than positive TPOAb in kits A-D (mean ± SD of the four kits: 98.6 ± 1.7 vs 81.4 ± 2.0%). In patients with Graves' disease, TgAb prevalence was almost equivalent to that of TPOAb in five kits. Patients with painless thyroiditis exhibited positive TgAb significantly more frequently than positive TPOAb in kits A-D (73.5 ± 4.1 vs 33.0 ± 3.4%). The prevalence of TgAb alone was significantly higher than that of TPOAb alone in both Hashimoto's thyroiditis and painless thyroiditis in kits A-D. In kit E, TgAb and TPOAb prevalence did not differ significantly for any disease, and TgAb distribution was different from other kits. In conclusion, the prevalence of TgAb was higher than that of TPOAb in patients with Hashimoto's thyroiditis and painless thyroiditis using commercially available kits. We suggest that TgAb immunoassay is the first choice of screening test for thyroid autoimmune abnormalities in Japan.

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.

Pediatric Reference Intervals for Free Thyroxine and Free Triiodothyronine by Equilibrium Dialysis-Liquid Chromatography-Tandem Mass Spectrometry

OBJECTIVE

Thyroid hormone concentrations fluctuate during growth and development. To accurately diagnose thyroid disease in pediatric patients, reference intervals (RIs) should be established with appropriate age groups from an adequate number of healthy subjects using the most exact methods possible. Obtaining statistically useful numbers of healthy patients is particularly challenging for pediatric populations. The objective of this study was to determine non-parametric RIs for free thyroxine (fT4) and free triiodothyronine (fT3) using equilibrium dialysis-high performance liquid chromatography-tandem mass spectrometry with over 2200 healthy children 6 months-17 years of age.

METHODS

Subjects were negative for both thyroglobulin and thyroid peroxidase autoantibodies and had normal thyrotropin concentrations. The study included 2213 children (1129 boys and 1084 girls), with at least 120 subjects (average of 125) from each year of life, except for the 6 month to 1 year age group (n=96).

RESULTS

Non-parametric RIs (95th percentile) for fT4 were: 18.0-34.7 pmol/L (boys and girls, 6 months-6 years) and 14.2-25.7 pmol/L (boys and girls, 7-17 years). RIs for fT3 were: 5.8-13.1 pmol/L (girls, 6 months-6 years); 5.7-11.8 pmol/L (boys, 6 months-6 years); 5.7-10.0 pmol/L (boys and girls, 7-12 years); 4.5-8.6 pmol/L (girls, 13-17 years); and 5.2-9.4 pmol/L (boys, 13-17 years).

CONCLUSION

Numerous significant differences were observed between pediatric age groups and previously established adult ranges. This emphasizes the need for well-characterized RIs for thyroid hormones in the pediatric population.

The upper reference limit for thyroid peroxidase autoantibodies is method-dependent: A collaborative study with biomedical industries

BACKGROUND

The determination of the upper reference limit (URL) for thyroid peroxidase autoantibodies (TPOAbs) is a contentious issue, because of the difficulty in defining the reference population. The aim of this study was to establish the URL (eURL) for TPOAbs, according to the National Academy of Clinical Biochemistry (NACB) guidelines and to compare them with those obtained in a female counterpart, by the use of six commercial automated platforms.

METHODS

120 healthy males and 120 healthy females with NACB-required characteristics (<30years, TSH between 0.5 and 2.0mIU/L, normal thyroid ultrasound, without personal/family history of thyroid and non-thyroid autoimmune diseases) were studied. Sera were analyzed for TPOAbs concentration using six immunoassay methods applied in automated analyzers: Advia Centaur XP (CEN), Siemens Healthcare Diagnostics; Maglumi 2000 Plus, Shenzen New Industries Biomedical Engineering; Architect ci4100, Abbott; Cobas e411 (COB) Roche Diagnostics; Unicel DxI (UNI) and Lumipulse G1200, Fujirebio.

RESULTS

Within each method, TPOAbs values had a high degree of dispersion and the eURLs were lower than those stated by the manufacturer. A statistically significant difference (p<0.05) between medians of males and females was observed only for COB and for UNI. However, the comparison of the male and female proportions positive for TPOAbs using the eURL of the counterpart, showed the lack of clinical significance of the above differences (Chi-square test, p>0.05).

CONCLUSIONS

Despite the analytical harmonization, the wide dispersion of the results and the differences of the eURLs between methods suggest the need of further studies focusing on TPO antigen preparations as the possible source of variability between different assays. In addition, the lack of clinical significant difference between males and females, in terms of TPOAb eURLs, confirms the suitability of the NACB recommendations.

Establishment of the upper reference limit for thyroid peroxidase autoantibodies according to the guidelines proposed by the National Academy of Clinical Biochemistry: comparison of five different automated methods

Aim of the study

The estimation of the upper reference limit (URL) for autoantibodies against thyroid peroxidase (TPOAbs) is a controversial issue, because of an uncertainty associated with the criteria used to correctly define the reference population. In addition, the URL of TPOAbs is method-dependent and often arbitrarily established in current laboratory practice. The aim of this study was to determine the reference limits of TPOAbs in a male sample according to the National Academy of Clinical Biochemistry (NACB) guidelines, and to compare them with those obtained in a female group, for five third-generation commercial-automated immunoassay (IMA) platforms.

Methods

120 healthy males and 120 healthy females with NACB-required characteristics (younger than 30 years, TSH between 0.5 and 2.0 mIU/L, normal thyroid ultrasound, absence of thyroid disease and absence of other autoimmune diseases) were studied. Sera were analyzed for TPOAbs concentration using five IMA methods applied in automated analyzers: Immulite 2000 XPi (IMM); Maglumi 2000 Plus (MAG); Kryptor Compact Plus (KRY); Phadia 250 (PHA) and Liaison XL (LIA).

Results

A statistically significant difference (p < 0.05) between medians in male and female groups was observed for PHA (2.6 and 3.1 IU/mL, respectively) but not for the other four methods. Scatter plots of TPOAbs values revealed a wide dispersion with very different coefficients of variation between the five methods, varying from 48.6 % for KRY in females to 126.3 % for MAG in females. The URLs differed in males and females according to the method: 28.7 and 29.0 IU/mL for IMM, 24.6 and 25.4 IU/mL for MAG, 6.4 and 6.9 IU/mL for KRY, 8.3 and 10.0 IU/mL for PHA and 14.2 and 17.9 IU/mL for LIA, respectively. Such URLs were lower than those stated by the manufacturers except for LIA in females. The difference between URLs ranged from a minimum of 11.3 % (LIA in males) to a maximum of 66.8 % (PHA in males).

Conclusions

Differences in URLs could result from the different coating preparations of the TPO antigen (purified native or recombinant) on solid phase, which affect the proper exposure of the immunodominant epitopes recognized by the polyclonal antibodies present in serum of patients with autoimmune thyroid disease (AITD). Based on these findings, we suggest to overcome the proposal of the NACB guidelines which recommend to involve a single group of young male subjects, and propose, instead, to utilize two distinct groups: one of males and one of females. This new proposal removes the apparent contrast of an all-male reference group for a disease (such as AITD) that affects mainly females. However, in spite of the harmonization among methods provided by the use of an international standard preparation, the wide dispersion of quantitative results still observed in this study suggests the need for further efforts to better understand the cause of these discrepancies, focusing on TPO antigen preparations as the possible source of variability among different assays.

Mechanisms in endocrinology: the crosstalk between thyroid gland and adipose tissue: signal integration in health and disease

Obesity and thyroid diseases are common disorders in the general population and they frequently occur in single individuals. Alongside a chance association, a direct relationship between 'thyroid and obesity' has been hypothesized. Thyroid hormone is an important determinant of energy expenditure and contributes to appetite regulation, while hormones and cytokines from the adipose tissue act on the CNS to inform on the quantity of energy stores. A continuous interaction between the thyroid hormone and regulatory mechanisms localized in adipose tissue and brain is important for human body weight control and maintenance of optimal energy balance. Whether obesity has a pathogenic role in thyroid disease remains largely a matter of investigation. This review highlights the complexity in the identification of thyroid hormone deficiency in obese patients. Regardless of the importance of treating subclinical and overt hypothyroidism, at present there is no evidence to recommend pharmacological correction of the isolated hyperthyrotropinemia often encountered in obese patients. While thyroid hormones are not indicated as anti-obesity drugs, preclinical studies suggest that thyromimetic drugs, by targeting selected receptors, might be useful in the treatment of obesity and dyslipidemia.

Gestational thyroid reference intervals in antibody-negative Chinese women

OBJECTIVES

The aim of this study is to establish gestation-specific reference intervals (GRIs) for thyroid function assays in pregnant Chinese women with ARCHITECT and compare them to other GRI studies.

DESIGN AND METHOD

Thyroid antibody negative pregnant Chinese women were enrolled and followed to establish GRIs for thyroid function by use of the Abbott ARCHITECT i2000SR analyzer (N=1409). Samples from 360 non-pregnant Chinese women served as controls.

RESULTS

GRIs of thyroid-stimulating hormone, free thyroxine and free triiodothyronine for first trimester pregnancies were 0.16-3.78mIU/L, 10.9-17.7pmol/L and 2.9-5.0pmol/L, respectively. GRIs for second trimester pregnancies were 0.34-3.51mIU/L, 9.3-15.2pmol/L and 2.9-4.6pmol/L. GRIs for third trimester pregnancies were 0.34-4.32mIU/L, 7.9-14.1pmol/L and 2.9-4.5pmol/L.

CONCLUSIONS

Our thyroid GRIs were different from those in other Chinese studies generated on other analyzers, but were similar to a Swiss study using the same analyzer. These data should prove useful for the interpretation of thyroid function assays among pregnant women measured on the Abbott analyzer.

Thyroglobulin antibody (TgAb) methods - Strengths, pitfalls and clinical utility for monitoring TgAb-positive patients with differentiated thyroid cancer

Thyroglobulin autoantibodies (TgAb) are detected at diagnosis or during treatment in approximately 25% of patients with differentiated thyroid cancer (DTC). When present, TgAb interferes with thyroglobulin (Tg) measurement causing falsely low or undetectable Tg immunometric assay (IMA) values that can mask disease. Guidelines mandate that every Tg test have TgAb measured simultaneously and quantitatively by immunoassay and not a recovery test. The propensity and magnitude of TgAb-Tg interference relates to both Tg and TgAb concentrations and the class of Tg method used. Because the TgAb trend reflects changes in thyroid tissue mass, TgAb concentrations serve as a surrogate post-operative DTC tumor marker. A rising, or de novo appearance of TgAb may indicate recurrence, whereas a progressive decline suggests successful treatment. This review focuses on the technical limitations of current TgAb methods, characteristics of TgAb interference with different classes of Tg method, and the clinical value of monitoring TgAb trends as a surrogate DTC tumor marker.

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.

The importance of having a flexible scope ISO 15189 accreditation and quality specifications based on biological variation--the case of validation of the biochemistry analyzer Dimension Vista

INTRODUCTION

Technological innovation requires the laboratories to ensure that modifications or incorporations of new techniques do not alter the quality of their results. In an ISO 15189 accredited laboratory, flexible scope accreditation facilitates the inclusion of these changes prior to accreditation body evaluation. A strategy to perform the validation of a biochemistry analyzer in an accredited laboratory having a flexible scope is shown.

MATERIALS AND METHODS

A validation procedure including the evaluation of imprecision and bias of two Dimension Vista analysers 1500 was conducted. Comparability of patient results between one of them and the lately replaced Dimension RxL Max was evaluated. All studies followed the respective Clinical and Laboratory Standards Institute (CLSI) protocols. 30 chemistry assays were studied. Coefficients of variation, percent bias and total error were calculated for all tests and biological variation was considered as acceptance criteria. Quality control material and patient samples were used as test materials. Interchangeability of the results was established by processing forty patients' samples in both devices.

RESULTS

27 of the 30 studied parameters met allowable performance criteria. Sodium, chloride and magnesium did not fulfil acceptance criteria. Evidence of interchangeability of patient results was obtained for all parameters except magnesium, NT-proBNP, cTroponin I and C-reactive protein.

CONCLUSIONS

A laboratory having a well structured and documented validation procedure can opt to get a flexible scope of accreditation. In addition, performing these activities prior to use on patient samples may evidence technical issues which must be corrected to minimize their impact on patient results.

Causes of discordance between thyroglobulin antibody assays

Background

Anti-thyroglobulin (Anti-Tg) assays show poor concordance.

Methods

We have investigated concordance and the causes of discordance between Abbott, Roche and Immulite Anti-Tg assays in 606 patients followed up for differentiated thyroid cancer (DTC). The reference range (RR) or lower reporting limit (LRL) was used to classify samples as negative or positive.

Results

Anti-Tg prevalence ranged between 6% and 55% depending on the method and cut-off. Concordance was 45% using LRL and 75% using RR. Specimens between the RR and LRL using the Immulite and Roche assays were identified that were positive by the Abbott assay and showed poor recovery of Tg in the Tg assay. This suggests misclassification using the RR. Anti-Tg International Reference Preparation (IRP) concentrations measured by the Roche and Abbott methods agreed well but patient samples did not. This is likely to be due to the heterogeneity of Anti-Tg. The Immulite assay appeared less sensitive than the Abbott and Roche based on investigations using the IRP and the low prevalence of Anti-Tg in the DTC patients (6–8%). Interference by Tg (>1000 μg/L) in the Roche assay was also identified as a cause of assay discordance.

Conclusions

Anti-Tg is used as a tumour marker for DTC and to predict interference in Tg assays themselves and hence inform clinicians of reported Tg concentrations. We have identified several causes of Anti-Tg assay discordance. This includes variation in assay sensitivity and interference from Tg, the heterogeneity of Anti-Tg and the use of different cut-offs to classify samples as antibody-positive or -negative.

The impacts of organochlorines and other persistent pollutants on thyroid and metabolic health

High prevalence of thyroid and metabolic disorders has been repeatedly observed in the population living in the area of eastern Slovakia highly polluted by a mixture of PCBs, DDE and HCB since about 50 years ago. Among thyroid disorders, increase of thyroid volume as measured by ultrasound volumetry may be suggested as one of notable findings which appeared possibly related to increased OCs levels and to autoimmunity signs (e.g. positive thyroperoxidase antibodies in blood and/or hypoechogenicity image obtained by ultrasound), while some participation of individual susceptibility and also of immunogenic effect of OCs and iodine in this iodine replete country cannot be excluded. Another notable finding has been the increase of blood FT4 and TT3 positively related to high PCBs level. Such increased FT4 level has been found associated with TSH level in hyperthyroid range in about 2% of examined population from polluted area. High prevalence of thyroid autoimmune disorders strongly supported the assumption on impaired immune system and thus also on presumably increased prevalence of other autoimmune disorders in highly exposed population. In addition, markedly increased prevalence of prediabetes and diabetes significantly related to major OCs (PCBs, DDE and HCB) levels and accompanied by increasing level of cholesterol and triglycerides has been observed. The observations also suggested a role of prenatal exposure to OCs in the development of several adverse health signs (e.g. increased prevalence of thyroid antibodies, impaired fasting glucose level, increased thyroid volume, decreased thymus volume, decreased neurobehavioral performance, increased hearing and dental disorders) in young generation born to highly exposed mothers in polluted area.

Definition of reference limits for autoantibodies to thyroid peroxidase and thyroglobulin in a large population of outpatients using an indirect method based on current data

CONTEXT

The reference limits for thyroid antibodies are generally made by measuring thyroid peroxidase and thyroglobulin antibody values in a group of healthy subjects (direct method), as proposed by the National Academy of Clinical Biochemistry.

OBJECTIVE

To define the upper reference limits of thyroid peroxidase and thyroglobulin, by using an indirect method to analyze data from a large number of outpatients that were stored in the information system of a general hospital laboratory.

DESIGN

Thyroid peroxidase and thyroglobulin values from 21 492 patients, who had undergone antithyroid antibody measurements, were retrieved from the laboratory information system; the upper reference limits (in the top 97.5 percentile) were calculated using the indirect Kairisto method, after exclusion of outliers.

RESULTS

The mean upper reference limits for females and males were 15 kIU/L and 9 kIU/L for thyroid peroxidase, and 21 kIU/L and 19 kIU/L for thyroglobulin, respectively. The upper limits showed minimal or no differences in the different age classes in either females or males.

CONCLUSIONS

Using a vast population of patients, we demonstrated that the upper limits for thyroid antibodies are much lower than the values obtained with classic, direct methods and that they do not vary in relation to age and sex.

Second-Trimester Reference Intervals for Thyroid Tests: The Role of Ethnicity

Background: Thyroid function changes during pregnancy, complicating the diagnosis of thyroid disorders. Maternal thyroid dysfunction has been associated with a variety of adverse outcomes. We evaluated thyroid function test results by ethnicity and week of gestation during the 2nd trimester of pregnancy.

Methods: We collected 3064 blood specimens in serum tubes from Asians (13%), blacks (22%), Hispanics (23%), and whites (42%). We measured thyroid-stimulating hormone (TSH), total and free thyroxine (TT4 and FT4), total and free triiodothyronine (TT3 and FT3), thyroglobulin autoantibodies (TgAb), and thyroid peroxidase autoantibodies (TPOAb) by use of an ARCHITECT i2000SR (Abbott Diagnostics). The TSH reference interval was calculated for samples negative for both TgAb and TPOAb and reference intervals for TT4, FT4, TT3, and FT3 in antibody-negative samples with normal TSH.

Results: Serum samples were positive for TgAb in 10.6%, 1.8%, 6.2%, 6.5%, and 5.9% of Asian, black, Hispanic, white, and combined groups, respectively. Samples were positive for TPOAb in 12.4%, 4.1%, 11.8%, 12.3%, and 10.4% of the same groups, respectively. The nonparametric reference intervals for all participants were 0.15–3.11 mIU/L (TSH), 9.3–15.2 pmol/L (0.72–1.18 ng/dL; FT4), 89.0–176.3 nmol/L (6.90–13.67 μg/dL; TT4), 3.82–5.96 pmol/L (2.48–3.87 pg/mL; FT3), and 1.82–3.68 nmol/L (118–239 ng/dL; TT3).

Conclusions: Blacks had lower prevalences of TgAb and TPOAb positivity and of increased serum TSH. The prevalence of TgAb and TPOAb positivity was highest in Asians. Whites had the highest prevalence of increased TSH. The lower and upper reference limits of TT3 were significantly lower for Asians. Reference intervals for women in the 2nd trimester were different from those of nonpregnant individuals.