ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2017) 49 EP1330 | DOI: 10.1530/endoabs.49.EP1330

Measurement of anti-thyroglobulin antibodies, a matter of equipment?

Ricardo Capitão1, Susana Prazeres2, Ana Font2, Conceição Godinho3, Isaura Rodrigues3, Frederico Cerveira4, Graça Belo1, João Viana1 & Deolinda Madureira5


1Hospital Egas MonizCentro Hospitalar Lisboa Ocidental, Lisboa, Portugal; 2Instituto Português de Oncologia de Lisboa Francisco Gentil, Lisboa, Portugal; 3Centro Hospitalar Lisboa Central, Lisboa, Portugal; 4Centro Hospitalar do Baixo Vouga, Aveiro, Portugal; 5Sociedade Portuguesa de Endocrinologia Diabetes e Metabolismo, Lisboa, Portugal.


Introduction: The presence of anti-thyroglobulin antibodies (ATG) can induce falsely lower thyroglobulin (Tg) values. The methods characteristics used for ATG measurement vary according to the equipment/reagent used. ATG at our centre is measured by Unicap.

Objective: To assess if patients with negative ATG by Unicap® have different results with other equipment.

Methods: A cross-sectional retrospective study was conducted in February-March of 2016, in which blood samples from patients followed at our Centre, with negative ATG, were selected and separated into three groups: 1) differentiated thyroid carcinoma (DTC), total thyroidectomy, Tg<0.2 ng/ml; 2) without DTC and positive TPO; 3) without DTC and negative TPO. ATGs were measured by Immulite®, Cobas®, Architect® and Advia®. ATG’s classification was based on the cut-off of each manufacturer. Q-Chrocan test was used to calculate the p-values (P<0.05 were considered statistically significant).

Results: A total of 141 samples were analysed. The results are described in the table below: high significant differences were found between the various methods in all groups. The Architect and the Immulite had the highest and lowest rate of ATG positives, respectively, compared to Unicap.

Table 1
Positive ATGQ test
GroupNUnicapImmuliteCobasArchitectAdviaχ2P
(A) DTC+/Tg<0.28801 (1%)3 (3%)23 (26%)6 (7%)70.0<0.001
(B) DTC−/TPO+2802 (7%)8 (29%)26 (93%)11 (39%)67.2<0.001
(C) DTC−/TPO−25001 (4%)6 (24%)2 (8%)17.70.001
Total14103 (2%)12 (9%)55 (39%)19 (14%)152.7<0.001

Discussion: ATG results depend on the equipment used. This can influence the follow-up strategy of patients with DTC. These results also raise the question of which method is more reliable for ATG detection and how a result of ‘ATG positive’ actually influences the Tg measurement.

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