Thyroglobulin, Tumor Marker Reflex, Serum
Use
The test is useful for measuring serum thyroglobulin (Tg) levels in patients with suspected or known antithyroglobulin antibodies or heterophile antibodies. It assists in the accurate reporting of thyroglobulin levels, providing valuable information for the follow-up of differentiated follicular cell-derived thyroid carcinoma. Serum Tg concentrations should be undetectable or very low after thyroidectomy in thyroid cancer patients. A concentration above 1 ng/mL in athyrotic individuals raises suspicion of residual or recurrent disease. Determining Tg levels following TSH stimulation enhances diagnostic accuracy.
Special Instructions
Patients should abstain from taking multivitamins or dietary supplements containing biotin (vitamin B7) for 12 hours before specimen collection. Use the Sarstedt Aliquot Tube, 5 mL (T914), for specimen submission. If not ordering electronically, complete and send an Oncology Test Request (T729) with the specimen.
Limitations
Presence of anti-thyroglobulin antibodies may interfere, leading to falsely low or high thyroglobulin measurements. Rare sequence variations in thyroglobulin can result in false-low results in mass spectrometry assays. Comparative measurements may reconcile discrepancies. Undetectable Tg levels require careful interpretation if antibodies are present. Tg concentrations above 250,000 ng/mL may be falsely low due to the 'hook' effect. Results from different methodologies may vary and should not be directly compared.
FDA ApprovedNew York Approved
Methodology
Immunoassay (Immunoenzymatic Assay)
Biomarkers
LOINC Codes
- 56536-6
- 56536-6
Result Turnaround Time
1-6 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2 mL
Minimum Volume
1.25 mL
Container
Red top tube preferred, plastic vial for submission
Collection Instructions
Centrifuge and aliquot serum into a plastic vial.
Patient Preparation
Do not take multivitamins or supplements containing biotin for 12 hours before collection.
Causes for Rejection
Gross hemolysis, gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 72 hours |
| Refrigerated | 7 days |
| Frozen | 30 days |