Tg and Tg Antibody Measurements in DTC Follow-Up

Lise Schoonen, Marjolein Neele, Hans van Toor, Caroline M J van Kinschot, Charlotte van Noord, W Edward Visser, Joost Groen, Lianne S M Boesten, Eef G W M Lentjes, Sjoerd A A van den Berg, Snjezana Kos
Journal of the Endocrine Society, Volume 6, Issue 1, January 2022, bvab166
https://doi.org/10.1210/jendso/bvab166

Abstract

Context

Measurements of thyroglobulin (Tg) and Tg antibodies are crucial in the follow-up of treated differentiated thyroid cancer (DTC) patients. Interassay differences may significantly impact follow-up.

Objective

The aim of this multicenter study was to explore the impact of Tg and Tg antibody assay performance on the differential classification of DTC patients, as described in national and international guidelines.

Design

Four commonly used Tg and Tg antibody assays were technically compared to reflect possible effects on patients with DTC follow-up. Storage stability at different storage temperatures was also investigated for LIAISON^® and Kryptor assays, as this is an underexposed topic in current literature.

Results

B.R.A.H.M.S. assays yield approximately 50% lower Tg values over the whole range compared to the DiaSorin and Roche assays investigated. These differences between assays may result in potential misclassification in up to 7% of patients if fixed cutoffs (eg, 1 ng/mL) are applied. Poor correlation was also observed between the Tg antibody assays when the method-specific upper limits of normal are used as cutoffs. Storage of Tg and Tg antibodies was possible for 3 to 4 weeks at −20°C and −80°C. Calibration of the assays, however, was found to be crucial for stable results over time.

Conclusions

Technical aspects of Tg and Tg antibody assays, including interassay differences, calibration and standardization, and cutoff values, may have a significant clinical impact on the follow-up of DTC patients.

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