Anti Thyroglobulin Antibody; HTG (Human Thyroglobulin); TG (Thyroglobulin); Thyroglobulin Antibody; Thyroglobulin Assay for Thyroid Cancer; Thyroglobulin HTC (Human Thyro)
Test ID
HTGR
General Information
Useful for:
Reporting of accurate thyroglobulin results, depending on the anti-thyroglobulin antibodies status of the patient
Accurate measurement of serum thyroglobulin in patients with known or suspected anti-thyroglobulin autoantibodies or possible heterophile antibodies
Testing Algorithm:
This test begins with the analysis of thyroglobulin antibody by immunoassay
If the thyroglobulin antibody result is negative (<1.8 IU/mL) thyroglobulin testing will be performed by immunoassay
If the thyroglobulin antibody result is positive (≥ 1.8 IU/mL) thyroglobulin testing will be performed by mass spectrometry
Specimen Type
Serum
Specimen Requirements
Red Top
Specimen Collection / Processing Instructions
Patient Preparation: For 12 hours before specimen collection do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins
Stability
Refrigerated (preferred: 7 days
Frozen: 30 days
Unacceptable Specimen Conditions
Gross hemolysis
Limitations
Thyroglobulin Antibody:
Antithyroglobulin values determined by different methodologies might vary significantly and cannot be directly compared with one another. Some patients might show to be antibody-positive by some methods and antibodynegative by others. Comparing values from different methods might lead to erroneous clinical interpretation
Thyroglobulin by Mass Spectrometry:
Rare normal amino acid sequence variations within thyroglobulin (Tg) can cause a false-low result in the Tg mass spectrometry assay, if they happen to be present in the Tg proteotypic peptides that are used for Tg quantification
While the exact prevalence of such changes is unknown, the validation data on large sample numbers indicate that this affects less than 1% of samples. In the heterozygote state, the result would be an apparent reduction in Tg concentration by about 50%, while the homozygous state (<0.01%) is predicted to result in total loss of signal. Therefore, if the results of the mass spectrometry measurement are much lower than those obtained previously (within 3-6 months) with an immunometric immunoassay, this possibility should be considered. In this event, alert Mayo Clinic Laboratories as soon as possible, and an attempt will be made to resolve the discrepancy
Thyroglobulin by Immunoassay:
Thyroid autoantibodies may interfere with the measurement of Tg by immunometric methods leading to an underestimation of the Tg present. Heterophile antibodies may also interfere. Specimens with thyroglobulin concentrations greater than 250,000 ng/mL may "hook" and appear to have markedly lower levels when assayed by immunoassay.
