Endocrine Abstracts

Introduction

Measurements of thyroglobulin (Tg) and Tg antibodies play a crucial role in the follow-up of treated differentiated thyroid cancer (DTC) patients, for instance to determine the response to therapy and the use of additional investigations and therapies. The aim of this study was to explore, from a laboratory perspective, the practical implications of the substantial clinical role of these measurements being imposed by national and international guidelines.^1–3

Methods

The newly released DiaSorin LIAISON Tg II assay and the corresponding Tg antibody assay, as well as the established BRAHMS Kryptor hTg and anti-Tgn assays, BRAHMS DYNOtest Tg-pluS IRMA assay, Roche Cobas Elecsys Tg II and anti-Tg assays and Phadia EliA anti-Tg assay, were evaluated and compared in the light of the recommended cut-off values indicated in the relevant guidelines. Additionally, storage stability of the markers was evaluated using different assays, as this is an underexposed aspect in the evaluation of Tg and Tg antibody assays that may have a significant impact on both the daily clinical use of the assays and the use of the assays in clinical studies.

Results

The Tg assays showed a maximum difference of a factor two. Between the different types of Tg antibody assays, a bad correlation was generally observed. In almost all method comparisons, disconcordant results were found looking at the appropriate cut-off values. Additionally, unique data was obtained regarding the storage stability of Tg and Tg antibodies using the assays described in this study.

Conclusion

Tg and Tg antibody assay differences could potentially have a significant clinical impact on the follow-up of DTC patients. Both clinicians and laboratory professionals should be aware of this and should use these measurements accordingly. This study is an example of how unavoidable, inherent assay differences of endocrinological markers complicate use of fixed cut-offs in the guidelines.

References

1. Haugen et al. Thyroid 2016, 26: 1.

2. Perros et al. Clin Endocrinol 2014, 81: Suppl 1.

3. Dutch guideline for thyroid carcinoma, https://www.oncoline.nl/schildkliercarcinoom.