Test ID: HTG1
Thyroglobulin, Tumor Marker, Serum
NY State Approved 
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Follow-up of patients with differentiated thyroid cancers after thyroidectomy and ablation
An aid in determining the presence of thyroid metastasis to lymph nodes
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| HTGS | Thyroglobulin, Tumor Marker, S | No | Yes |
| TGABS | Thyroglobulin Antibody Screen, S | No | Yes |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
All specimens are screened for the presence of autoantibody to thyroglobulin.
Method Name A short description of the method used to perform the test
HTGS/23745: Immunoenzymatic Assay
TGABS/32472: Electrochemiluminescence Immunoassay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
HTG (Human Thyroglobulin)
TATC (Thyroglobulin Assay for Thy Cancer)
TG (Thyroglobulin)
Thyroglobulin Antibody
Thyroglobulin Assay for Thyroid Cancer
Thyroglobulin HTC (Human Thyro)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Specimen Volume: 1.5 mL
Forms: If not ordering electronically, submit a General Request Form (Supply T239) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross OK |
| Icterus | NA |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 7 days |
| Frozen | 30 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Thyroglobulin (Tg) is a glycoprotein (660,000 MW) composed of 2,748 amino acids, which contains 8% to 10% carbohydrate and iodine. The amount of iodine varies with the dietary intake of the individual. Seventy percent of the Tg monomer is composed of repeat sequences.
Tg is present in the serum of normal individuals. It is secreted only by the thyroid gland and composes about 75% of the total protein of thyroid follicular colloid. The thyroid hormones thyroxine (T4) and triiodothyronine (T3) are synthesized from tyrosine residues of Tg in the thyroid epithelial cell. T4 and T3 are released after Tg is endocytosed and proteolytically degraded in the thyrocyte. Tg itself is not biologically active.
Thyroid cancer is commonly treated by surgical removal of the thyroid gland, often followed by ablation of the thyroid remnant. Patients receive lifelong thyroid hormone replacement therapy. Traditionally, (131)iodine scanning is used to detect residual disease. More recently, this approach has been supplemented, and often supplanted, by measurement of serum Tg concentrations.
Serum Tg concentrations are very low or undetectable in athyrotic individuals. In the absence of a significant thyroid remnant, elevated or rising serum Tg levels are suspicious of recurrent or persistent disease. It is usually unnecessary to withhold thyroid hormone replacement prior to Tg testing. However, to optimize the ability to detect recurrent disease, thyroid replacement is often withheld prior to Tg testing, or recombinant thyrotropin is administered, particularly if the patient also is undergoing (131)iodine scanning. Thyroid-stimulating hormone (TSH) increases Tg production and iodine uptake of any benign or malignant residual thyroid tissue.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
THYROGLOBULIN, TUMOR MARKER
> or =16 years: < or =33 ng/mL
Athyrotic individuals normally have human thyroglobulin values < or =2 ng/mL.
THYROGLOBULIN ANTIBODY SCREEN
<22 IU/mL
Reference values apply to all ages.
Interpretation Provides information to assist in interpretation of the test results
Thyroglobulin (Tg) antibody screening is performed to rule out interference in the Tg assay. Values <22 IU/mL are considered normal and unlikely to cause interference.
All of the following interpretative suggestions for serum Tg apply only to patients who do not have elevated serum Tg autoantibodies:
-The American Thyroid Association guidelines for the management of differentiated thyroid cancer suggest that athyrotic thyroid cancer patients (total thyroidectomy and radioiodine remnant ablation) should have unstimulated (on thyroxine [T4]) and stimulated (thyroid hormone withdrawal or recombinant human thyroid-stimulating hormone [TSH] stimulation) serum Tg concentrations < or =2 ng/mL. Patients with higher levels should be investigated for persistent or recurrent disease.
-Athyrotic thyroid cancer patients with unstimulated or stimulated serum Tg concentrations >10 ng/mL are likely to have evidence of persistent or recurrent disease.
-In athyrotic low-risk thyroid cancer patients, recent evidence suggests that serum Tg levels <0.1 ng/mL, combined with neck ultrasound, obviate the need for stimulated Tg testing.
-For patients with small thyroidal remnants there are currently no universally accepted cutoff levels for Tg. It has been suggested that Tg levels should not exceed approximately 0.5 ng/mL per gram of remnant tissue in patients with suppressed TSH (<0.3 mIU/L), or approximately 1 ng/mL if TSH is in the normal reference range (0.3-5 mIU/L).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The test is most sensitive for detection of thyroid cancer recurrence when patients are off thyroid replacement long enough to have an elevated thyroid-stimulating hormone (TSH) prior to drawing the specimen. This test also can be used to follow patients with normal TSH; however, thyroglobulin (Tg) values from specimens with high TSH should not be compared with values with normal TSH, because TSH stimulation changes the baseline determinations.
Thyroid autoantibodies may interfere with the measurement of Tg. All specimens are prescreened for antibodies and a comment appended to the report if they are present. Undetectable levels of Tg should be interpreted with caution if anti-Tg is present. A Tg antibody result of <22 IU/mL is unlikely to cause clinically significant Tg assay interference. It is recommended that the Tg result be reviewed for concordance with clinical presentation
Specimens with Tg concentrations >250,000 ng/mL may "hook" and appear to have markedly lower levels.
Anti-Tg values determined by different methodologies might vary significantly and cannot be directly compared with one another. Some patients might be antibody-positive by some methods and antibody-negative by others. Comparing anti-Tg antibodies values from different methods might lead to erroneous clinical interpretation.
In patients receiving therapy with high biotin doses (ie, >5 mg/day), no specimen should be drawn until at least 8 hours after the last biotin administration
Tg concentrations >2,000 ng/mL may lead to falsely elevated anti-Tg concentrations. In this case, anti-Tg concentrations may be unreliable.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Cooper DS, Doherty GM, Haugen BR, et al: American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer. Thyroid 2009;19:1167-1214
2. Smallridge RC, Meek SE, Morgan MA, et al: Monitoring thyroglobulin in a sensitive immunoassay has comparable sensitivity to recombinant human TSH- stimulated thyroglobulin in follow-up of thyroid cancer patients. J Clin Endocrinol Metab, 2007;92:82-87
3. Torrens JI, Burch HB: Serum Thyroglobulin measurement. Utility in Clinical Practice. Endocrinol Metab Clin North AM 2001 June;30(2):429-467
4. National Academy of Clinical Biochemistry: Laboratory Medicine Practice Guidelines. Edited by LM Demers, CA Spencer. Laboratory support for the diagnosis and monitoring of thyroid disease, Section D. Thyroid antibodies (TPOAb, TgAb, TRAb), pp 43-54, and Section E. Thyroglobulin (Tg), pp 55-65-reprinted in unchanged form in Thyroid 2003;13(1):45-56, 57-67
Method Description Describes how the test is performed and provides a method-specific reference
The Beckman Coulter UniCel DxI 800 is used for thyroglobulin tumor marker testing. The Access Thyroglobulin (Tg) assay is a simultaneous 1-step immunoenzymatic ("sandwich") assay. A sample is added to a reaction vessel, along with a biotinylated mixture of 4 monoclonal anti-Tg antibodies, streptavidin-coated paramagnetic particles, and monoclonal anti-Tg antibody alkaline phosphatase conjugate. The biotinylated antibodies and the serum Tg binds to the solid phase, while the conjugate antibody reacts with a different antigenic site on the Tg molecule. After incubation in a reaction vessel, materials bound to the solid phase are held in a magnetic field while unbound materials are washed away. Then, the chemiluminescent substrate Lumi-Phos* 530 is added to the vessel and light generated by the reaction is measured with a luminometer. The light production is directly proportional to the concentration of Tg in the sample. The amount of analyte in the sample is determined from a stored, multipoint calibration curve.(Beckman Coulter Assay Manual, 2010)
Thyroglobulin antibody testing is performed on a Roche Cobas instrument. The Roche Thyroglobulin Antibody assay (anti-Tg) is a competitive assay using electrochemiluminescence detection. Patient specimen is incubated with biotinylated Tg and antibodies in the sample bind to the antigen in the reagent. Anti-Tg antibodies labeled with ruthenium complex and streptavidin-coated microparticles are added and the immunocomplex produced becomes bound to the solid phase by interaction of biotin and streptavidin. The reaction mixture is aspirated into the measuring cell where the microparticles are magnetically captured onto the surface of the electrode. Unbound substances are then removed with ProCell. Application of a voltage to the electrode induces the electrochemiluminescent emission. This signal is measured against a calibration curve to determine patient results.(Package insert: Roche Cobas. Roche Diagnostics, Indianapolis, IN 2010)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday 5 a.m. – 12 a.m., Saturday 6 a.m. - 6 p.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
84432-Thyroglobulin, tumor marker
86800-Thyroglobulin antibody screen
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| HTGN | Thyroglobulin, Tumor Marker, S | 3013-0 |
| TGAB1 | Thyroglobulin Antibody Screen, S | 8098-6 |
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