Characterization of a new highly sensitive immunometric assay for thyroglobulin with reduced interference from autoantibodies

Predictive value and dynamic risk stratification of high sensitive basal or stimulated thyroglobulin assay in a long-term thyroid carcinoma cohort

PURPOSE

To evaluate the predictive value of the rhTSH thyroglobulin stimulation test (rhTSH-Tg) compared to basal high-sensitive thyroglobulin (hs-Tg) under TSH suppressive therapy at 12 months after the completion of initial treatment to predict the long-term response and Dynamic Risk Stratification (DRS) at the last follow-up visit in a long-term DTC cohort.

METHODS

Prospective study in 114 DTC patients (77.2% women, mean age 46.4 ± 14.1 years old, median/IQR evolution 6.7[3.1-8.0] years) from 2013 to 2020 undergoing total thyroidectomy and radioiodine ablation in whom hs-Tg and rhTSH-Tg was performed 12 months after completing initial treatment. Pearson correlation, receiving operating characteristics (ROC) and DRS at initial and last follow-up visit were analyzed.

RESULTS

hs-Tg and rhTSH-Tg show a strong positive linear correlation (r = 0.864, p < 0.001). The diagnostic performance of initial hs-Tg and rhTSH-Tg levels were evaluated via ROC-AUC as a predictor of excellent response (ER) in the last follow-up visit. Hs-Tg showed a better AUC (0.969, 95%CI = 0.941-0.997) than rhTSH-Tg (0.944, 95%IC = 0.905-0.984; p < 0.001). The hs-Tg and rhTSH-Tg cutoff point of highest sensitivity (S) and specificity (E) was 0.110 and 0.815 ng/dl, respectively. Hs-Tg showed a higher diagnostic accuracy than rhTSH-Tg (S = 100% vs 96.8%, E = 84.3% vs 84.3%, NPV = 100% vs 98.6%, PPV = 70.5% vs 69.7%; p < 0.05). The DRS based on initial hs-Tg showed better ability to predict ER (93.3% vs 86.7%) and biochemical incomplete response (53.3%vs13.3%) in the last follow-up visit compared to rhTSH-Tg.

CONCLUSIONS

Both initial hs-Th and rhTSH-Tg were good predictors of long-term ER. In patients with hs-Tg, the rhTSH-test did not provide relevant prognosis information. An ER after initial treatment was associated with a very high NPV at subsequent follow-up.

Long-Term Efficacy of Ethanol Ablation as Treatment of Metastatic Lymph Nodes From Papillary Thyroid Carcinoma

CONTEXT

Ethanol ablation (EA) is considered an alternative to surgery for metastatic lymph nodes from papillary thyroid carcinoma (PTC) in selected patients.

OBJECTIVE

The aim of this study was to evaluate the long-term efficacy and safety of this treatment.

DESIGN AND SETTING

Adult patients with PTC who had received EA in lymph node metastasis at a tertiary referral center, and were included in a published study from 2011, were invited to participate in this follow-up study.

METHODS

Radiologic and medical history were reviewed. Ultrasound examination of the neck was performed by radiologists, and clinical examination was performed by an endocrine surgeon. Response was reported according to predefined criteria for satisfactory EA treatment. Adverse events associated with EA were evaluated. Cause of death was reported for deceased patients.

RESULTS

From the 2011 study, 51 of 63 patients were included. Forty-four patients were reexamined (67/109 lesions) and 7 patients were deceased. Median follow-up time from primary surgery was 14.5 years. Median follow-up from the latest performed EA in the 2011 study was 11.3 years. Local control was permanently achieved in most patients (80%). Recurrence within an ablated node was registered in 13 metastases in 10 patients. Seven of these patients also had recurrent disease elsewhere in the neck. No major side effects were reported.

CONCLUSION

EA is a minimally invasive procedure with a low risk of complications. Our data suggest that EA is a safe and efficient treatment, providing excellent results for a large group of patients in the long term.

Biotin Interference in Assays for Thyroid Hormones, Thyrotropin and Thyroglobulin

Background: Biotin has been reported to interfere with several commonly used laboratory assays resulting in misleading values and possible erroneous diagnosis and treatment. This report describes a prospective study of possible biotin interference in thyroid-related laboratory assays, with a comparison of different commonly used assay platforms. Materials and Methods: Thirteen adult subjects (mean age 45 ± 13 years old) were administered biotin 10 mg/day for eight days. Blood specimens were collected at three time points on day 1 and on day 8 (baseline, two, and five hours after biotin ingestion). Thyrotropin (TSH), free triiodothyronine (fT3), free thyroxine (fT4), total triiodothyronine (TT3), total thyroxine (TT4), thyroxine binding globulin (TBG), and thyroglobulin (Tg) levels were analyzed with four different platforms: Abbott Architect, Roche Cobas 6000, Siemens IMMULITE 2000, and liquid chromatography with tandem mass spectrometry (LC-MS/MS). TSH, fT3, fT4, TT3, and TT4 were measured with Abbott Architect and Roche Cobas 6000. fT3, fT4, TT3, and TT4 were also measured by LC-MS/MS. Tg was measured by Siemens IMMULITE 2000. TBG was assessed with Siemens IMMULITE 2000. Results: Significant changes in TSH, fT4, and TT3 measurements were observed after biotin exposure when the Roche Cobas 6000 platform was used. Biotin intake resulted in a falsely lower Tg level when measurements were performed with Siemens IMMULITE 2000. At the time points examined, maximal biotin interference was observed two hours after biotin exposure both on day 1 and day 8. Conclusions: A daily dose of 10 mg was shown to interfere with specific assays for TSH, fT4, TT3, and Tg. Physicians must be aware of the potential risk of erroneous test results in subjects taking biotin supplements. Altered test results for TSH and Tg can be particularly problematic in patients requiring careful titration of levothyroxine therapy such as those with thyroid cancer.

Highly sensitive electrochemical immunosensor using a protein-polyvinylidene fluoride nanocomposite for human thyroglobulin

The highly sensitive detection of serum thyroglobulin (Tg) is essential in the post-treatment follow-up of patients with differentiated thyroid cancer undergoing total or partial thyroidectomy and radioactive iodine ablation and requires sensitive, accurate and stable methods. This work proposes an electrochemical immunosensor for the detection of serum Tg antigen, making use of innovative nanocomposites including polyvinylidene fluoride (PVDF) microparticles coated with streptavidin (MP) and gold nanoparticles (AuNPs). The functionalized polymer matrices were characterized by UV-Vis, FTIR, XPS, SEM, dynamic light scattering, and free surface energy. Immobilization of biotin-labeled anti-thyroglobulin monoclonal antibodies was achieved by binding these to the polymer nanocomposite via streptavidin proteins. The analytical response was measured in quintuplicate and had a linear profile from 2.0 to 10.0 ng/mL Tg, with r² of 0.985. The limits of detection and quantification were excellent, equal to 0.015 and 0.047 ng/mL, respectively. In addition, the recovery factor was equal to 95.4% (1.0 ng/mL Tg). Overall, the innovative polymer-based nanocomposite used herein enabled the production of an electrochemical-based immunosensor with excellent sensitivity, selectivity, and reproducibility. It evidenced the remarkable potential of determining low levels of Tg in in vitro assays, thereby suggesting that it may be considered for the analyzes of serum patients.

Liquid chromatography mass spectrometry based characterization of epitope configurations

Here we evaluate a quick and easy tool for determination of epitope configuration using immunocapture and liquid chromatography mass spectrometry (LC-MS) subsequent to pre-treatment of the target protein to disrupt its three-dimensional structure. The approach can be a valuable screening tool to identify antibodies that can be used in peptide capture by anti-protein antibodies. The experimental set-up was established using seven monoclonal antibodies (mAbs) with known linear or conformational epitope recognition. The mAbs were developed to target either of the two biomarkers, progastrin releasing peptide (ProGRP) or human chorionic gonadotropin (hCG). Best coherence with established epitope configuration was seen when using both denaturation, reduction and alkylation as pre-treatment method of the proteins (≥70% reduction in MS signal intensity compared to control) prior to immunocapture and LC-MS determination. The final method was used to determine the epitope configuration of four anti-thyroglobulin mAbs with unknown epitope configuration; all four mAbs showed configurational epitope recognition. These results were also supported by western blots of native, and reduced and alkylated protein using three of the evaluated mAbs, and by analysis native, and reduced and alkylated protein in a routine immunofluorometric assay employing the four evaluated antibodies.

Comparison between a new thyroglobulin assay with the well-established Beckman Access immunoassay: A preliminary report

OBJECTIVES

Measurement of serum thyroglobulin (Tg) plays a key role in the post-thyroidectomy management of differentiated thyroid carcinoma (DTC). In this context, the performance of new-generation thyroglobulin assay has clinical implications in the follow-up of DTC patients. Aim of this study was to compare the new highly sensitive Liaison Tg II (Tg-L) with the well-established Tg Access assay (Tg-A).

MATERIALS AND METHODS

A total of 91 residual serum samples (23 positive and 68 negatives for Tg auto-antibodies) were tested by the Beckman Access and Diasorin Liaison assays. Study samples were from 21 patients with pathologically proven DTC and control samples from 70 (16 patients with benign thyroid disease and 54 apparently healthy subjects).

RESULTS

Our results showed that Tg-L was highly correlated with Tg-A for both values ranging between 0.2 and 50 ng/mL (Pearson's r = 0.933 [95%CI 0.894-0.958], P < .001) and higher than 50 ng/mL (Pearson's r = 0.849 [95%CI 0.609-0.946], P < .001). For Tg values lower than 0.2 ng/mL, the overall concordance rate was 92%. Moreover, we tested 7 fine-needle aspiration washout fluids (FNA), showing an overall concordance rate in discriminating negative and positive of 100%. Finally, we found no interference by Tg auto-antibodies (TgAbs) for both Tg-L and Tg-A. Conversely, rheumatoid factor (RF) interferes with Tg-A, but not with Tg-L in one patient with no relapsing thyroid carcinoma.

CONCLUSIONS

Liaison Tg II demonstrated a good correlation with Access Tg assay both for sera and FNAs. Further studies on larger population are needed to evaluate Tg-L clinical impact on DTC patient's follow-up.

Specific antibodies and sensitive immunoassays for the human epidermal growth factor receptors (HER2, HER3, and HER4)

The use of trastuzumab in patients with breast cancer that overexpresses human epidermal growth factor receptor 2 has significantly improved treatment outcomes. However, a substantial proportion of this patient group still experiences progression of the disease after receiving the drug. Evaluation of the changes in expression of the human epidermal growth factor receptors could be of interest. Monoclonal antibodies against the extracellular domain of the human growth factor receptors, 2, 3, and 4, have been raised, and specific and sensitive immunoassays have been established. Sera from healthy individuals (Nordic Reference Interval Project and Database) were analyzed in the human epidermal growth factor receptor 2 assay (N = 805) and the human epidermal growth factor receptor 3 and 4 assays (N = 114), and reference limits were calculated. In addition, sera from 208 individual patients with breast cancer were tested in all three assays. Finally, the human epidermal growth factor receptor 2 assay was compared with a chemiluminescent immunoassay for serum human epidermal growth factor receptor 2/neu. Reference values were as follows: human epidermal growth factor receptor 2, <2.5 µg/L; human epidermal growth factor receptor 3, <2.8 µg/L; and human epidermal growth factor receptor 4, <1.8 µg/L. There were significant differences in human epidermal growth factor receptor 2 and human epidermal growth factor receptor 3 serum levels between the patients with tissue human epidermal growth factor receptor 2-positive and tissue human epidermal growth factor receptor 2-negative ( p = 0.0026, p = 0.000011) tumors, but not in the serum levels of human epidermal growth factor receptor 4 ( p = 0.054). There was good agreement between the in-house human epidermal growth factor receptor 2 assay and the chemiluminescent immunoassay. Our new specific antibodies for all the three human epidermal growth factor receptors may prove valuable in the development of novel anti-human epidermal growth factor receptor targeted therapies with sensitive immunoassays for measuring serum levels of the respective targets and in monitoring established treatment.