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Test Code TGTM Thyroglobulin Tumor Marker Cascade

Important Note

Human anti-mouse antibodies (HAMA) may be present in samples from patients who have received immunotherapy utilizing monoclonal antibodies. Additionally, other heterophile antibodies such as human anti-goat antibodies may be present in patient samples. Manufacturers formulate assays to minimize the effects of these antibodies, however careful evaluation of patient results must be done when patients are known to have such antibodies.

Access Thyroglobulin: potential of falsely decreased results when biotin concentrations are > 10 ng/mL.

Additional Codes

ALAB:  TGTM
Powerchart: Thyroglobulin Level
MA Cerner: Thyroglobulin, Tumor Marker

Test Method

Two-site immunoassay (Beckman Coulter):

Thyroglobulin Antibody

Thyroglobulin

Specimen Requirement

0.5 mL red top serum is the specimen of choice. Gel tubes are also acceptable but cannot be used for possible reflex testing sent to Mayo.

Additional Specimen Collection Information

Collection Instructions:
• Minimum volume: 500mcL serum.
• Hemolysis: does not interfere with this assay.
• Lipemia: does not interfere with this assay.
• Icterus: Samples with total bilirubin concentrations greater than 10 mg/dL should be interpreted with caution.
• Storage: Can be stored at room temperature for up to 8 hours. If specimens are stored longer than 8 hours keep refrigerated (2-8C) until transport to the lab.

Performance

Testing is performed Monday through Sunday.
Routine: Typically completed within 4 hours after the specimen arrives at the testing site.
STAT: Typically completed within 1 hour after the specimen arrives at the testing site.

Reference Value

Thyroglobulin Antibody:

< 4.0 IU/mL

Thyroglobulin:

Athyrotic: < 0.1 ng/mL
Intact Thyroid: < 33 ng/mL
Reference values apply to all ages.

Thyroglobulin is performed by this method if the Thyroglobulin antibody level is <4.0 IUmL. If the thyroglobulin antibody is >4.0 the thyroglobulin assay is sent to Mayo for assay by mass spectometry. 

 

CPT Code Information

84432 - Thyroglobulin

86800 - Thyroglobulin Antibody

Useful For

Thyroglobulin is present in the serum of normal healthy individuals and can be elevated in numerous disorders which disrupt thyroid tissue. Elevated circulating levels of Tg have been reported in a number of thyroid conditions including Hashimoto’s disease, Graves’ disease, thyroid adenoma, subacute thyroiditis and thyroid carcinoma.

Thyroid cancer is a relatively common form of cancer. It is not generally highly malignant, and normal life span can be obtained with appropriate follow-up and treatment. Females are affected 2 to 3 times more frequently than males. Thyroglobulin has become a useful tool in the follow-up of patients with differentiated thyroid carcinoma. The thyroid is the only source of Tg; therefore, the serum Tg level will drop to a very low or undetectable level after total or near-total thyroidectomy and successful radioiodine ablation of the residual thyroid tissue. A rise in the serum level of Tg points to the recurrence of the disease. Thyroglobulin levels in patients who have undergone only a partial thyroidectomy will retain measureable levels of Tg, depending on how much tissue is remaining after surgery. These patients can be monitored by Tg measurement, but the post-surgical Tg level must be taken in account.

A limiting factor in the use of serum Tg measurements is the presence of Tg autoantibodies found in some patients. These antibodies may interfere with the immunoassay used to measure Tg and can cause false high or false low values. It is important to determine the levels of Tg autoantibodies in patients requiring serum Tg measurements.