Related Experiment Video
Updated: Apr 12, 2026

Generation of a Mouse Spontaneous Autoimmune Thyroiditis Model
Published on: March 17, 2023
False positive in the measurement of thyroglobulin induced by rheumatoid factor
G Astarita1, S Gutiérrez2, N Kogovsek2
1Endocrinology Division, Durand Hospital, Buenos Aires, Argentina..
Background:
We report a case of interference in thyroglobulin (Tg) measurement in a woman with differentiated thyroid cancer and rheumatoid arthritis history. Due to discordant Tg in relation to TSH concentrations and negative images, we investigated possible interference in the measurement of Tg.
Methods:
During the follow-up we measured Tg by chemiluminescence (TgQL) using Immulite 2000 immunoassay system. To investigate possible interference in Tg measurement, we made serial dilutions, re-testing of Tg by an alternative method: electrochemiluminescence, Cobas 6000 analyzer (TgEQL), recovery test of Tg and polyethylene glycol (PEG) 6000 precipitation.
Results:
During the patient follow-up, the TgQL ranged between <0.3 and 16.1ng/ml. In the evaluated serum samples very high titers of rheumatoid factor (RF) were found. When RF titers were lowered post PEG precipitation, Tg QL concentrations became undetectable.
Conclusion:
We describe an unusual case of interference in Tg assay due to RF. When disagreement among Tg concentrations, images and clinical features is observed, we suggest taking into account the evaluation of possible Tg interference to avoid unnecessary complementary exams and inappropriate treatment.
More Related Videos
10:16Generation of Two-color Antigen Microarrays for the Simultaneous Detection of IgG and IgM Autoantibodies
Published on: September 15, 2016
10:27Recognition of Epidermal Transglutaminase by IgA and Tissue Transglutaminase 2 Antibodies in a Rare Case of Rhesus Dermatitis
Published on: December 15, 2011
Related Concept Videos
Synthesis and Regulation of Thyroid Hormones
Upon reaching the thyroid gland, TSH stimulates the follicular cells' active uptake of iodide ions from the blood. The ions diffuse to the apical surface of the cells and are oxidized to iodine. The...
Rheumatic Heart Disease II: Clinical Manifestations and Diagnostic Studies
Pulmonary Tuberculosis IV
Several diagnostic approaches are used to detect TB. The conventional method is the Tuberculin Skin Test (TST), also known as the Mantoux test. However, this method has...
Myasthenia Gravis: Diagnostic Tests
The edrophonium test is a diagnostic tool for myasthenia gravis. It involves...