Automated Assays Evaluated For High-Sensitivity Thyroglobulin Measurement

Over the past decade, assays for highly sensitive Tg measurement have become increasingly established.

Differentiated thyroid carcinoma, namely papillary and follicular thyroid carcinoma, makes up about 94% of these cases. Despite the generally good prognosis of thyroid carcinoma, about 5% of patients will develop metastatic disease which fails to respond to radioactive iodine, exhibiting a more aggressive behavior.

Clinical Laboratorians at the University Hospital of Essen (Essen, Germany) and their associate determined Tg values of 166 sera from subjects without thyroid diseases and of more than 500 sera of well-defined DTC patients. Histologically diagnosed papillary, follicular, oncocytic (Hürthle cell), or poorly differentiated thyroid carcinomas are referred to as thyroid follicular cell-derived differentiated thyroid carcinomas (DTC). The study groups were divided in separate cohorts and sub-groups.

To measure the Tg the investigators compared three different assays. The Medizym Tg Rem assay (Medipan, Blankenfelde-Mahlow, Germany), which is a manual two-step sandwich immunoenzymometric assay (IEMA) with two monoclonal antibodies directed against different epitopes of the Tg molecule. For the measurement of Tg values that are above the functional measuring range of the Tg Rem assay, they used in the Medipan SELco Tg assay, a manual immunoradiometric assay (IRMA) with two monoclonal antibodies.

The team also compared the Elecsys Tg II (Roche, Basel, Switzerland) which is an electrochemiluminescence immunoassay (ECLIA) for the Cobas automated system which uses biotinylated monoclonal Tg-specific antibodies and monoclonal Tg-specific antibodies labeled with a ruthenium complex that form a sandwich complex with Tg molecules in the sample. The other assay was the LIAISON Tg II Gen assay was run on a LIAISON XL analyzer (DiaSorin, Saluggia, Italy). The LIAISON XL analyzer is a fully automated chemiluminescence analyzer that adopts a “flash” chemiluminescence technology (CLIA) with paramagnetic microparticle solid phase. TgAb determinations were performed on the Immulite 2000XPi Immunoassay system (Siemens Healthineers, Eschborn, Germany).

The scientists reported that Tg reference values from healthy subjects were up to 37.93 ng/mL (women) and 24.59 ng/mL (men) with the LIAISON Tg II Gen assay. Tg values showed good correlations in healthy subjects and patients with active tumorous disease. In contrast, Tg values in the very low range from cured thyroidectomized patients were poorly comparable between the three assays, while clinical differences between the cohorts were correctly reflected by all assays.

The authors concluded that the data from their study demonstrated that with the new LIAISON Tg II Gen assay another assay running on an automated laboratory platform for measurement of Tg values ranging from the highly sensitive up to a pronounced increased level is available. In TgAb sera of DTC patients depicted different results between assays indicating different interferences of TgAb's with assay antibodies. The study was published on July 27, 2021 in the journal Practical Laboratory Medicine.

Related Links:

University Hospital of Essen 
Medipan
Roche 
DiaSorin
Siemens Healthineers