Thyroglobulin Antibodies (Autoimmune Thyroiditis)
| Label Mnemonic: | TGAB |
| Epic code: | LAB956 |
| Order form: | Laboratory Requisition |
| Supply order: | Supply Order Form |
| Billing: | Billing Policies |
| CPT code: | 86800 |
Specimen(s):
Plasma
Collection Medium:
 |
| Pink top tube 6 mL (K2-EDTA) |
Alternate
Collection Media:
Red top tube 5 mL (Clot Activator)
Minimum:
3 mL whole blood in pink top tube or TWO Microtainer®
devices.
Testing
Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around
Time:
1 hour (upon receipt in laboratory)
Reference Range:
<116 IU/mL
Reference values apply to all ages.
Reference values apply to all ages.
Interpretive Data:
Diagnosis of Autoimmune Thyroid Disease:
Measurements of anti-thyroid peroxidase (anti-TPO) autoantibodies have higher sensitivity and equal specificity to anti-thyroglobulin (anti- Tg) autoantibody measurements in the diagnosis of autoimmune thyroid disease. Anti-Tg autoantibody levels should, therefore, only be measured if anti-TPO autoantibody measurements are negative, but clinical suspicion of autoimmune thyroid disease is high.
Positive thyroid autoantibody levels in patients with high-normal or slightly elevated serum thyrotropin levels predict the future development of more profound hypothyroidism.
Patients with postpartum thyroiditis with persistently elevated thyroid autoantibody levels have an increased likelihood of permanent hypothyroidism.
In cases of neonatal hypothyroidism, the detection of anti-TPO or anti- Tg autoantibodies in the infant suggests transplacental antibody transfer, particularly if the mother has a history of autoimmune thyroiditis or detectable thyroid autoantibodies. The neonatal hypothyroidism is likely to be transient in these cases.
Thyroid Cancer Follow-Up:
Following therapy of differentiated follicular-cell derived thyroid cancer, all patients who have no, or only trivial, amounts of normal residual thyroid tissue and no persistent or recurrent cancer will have undetectable or very low serum thyroglobulin (Tg) levels. Persistently elevated or rising serum Tg levels, either on or off thyroxine replacement therapy, suggest possible tumor persistence or recurrence. However, if a patient also has measurable anti-Tg autoantibody levels >= 22 IU/mL, the results of serum Tg measurements are unreliable. Anti-Tg autoantibodies may result in both falsely-low and, less commonly, falsely-high serum Tg measurements. Therefore, in anti-Tg-positive patients, serum Tg measurements should either not be used in thyroid cancer follow-up or be interpreted with extreme caution. A thyroglobulin antibody result of <22 IU/mL is unlikely to cause clinically significant thyroglobulin assay interference. It is recommended that the thyroglobulin result be reviewed for concordance with clinical presentation.
Measurements of anti-thyroid peroxidase (anti-TPO) autoantibodies have higher sensitivity and equal specificity to anti-thyroglobulin (anti- Tg) autoantibody measurements in the diagnosis of autoimmune thyroid disease. Anti-Tg autoantibody levels should, therefore, only be measured if anti-TPO autoantibody measurements are negative, but clinical suspicion of autoimmune thyroid disease is high.
Positive thyroid autoantibody levels in patients with high-normal or slightly elevated serum thyrotropin levels predict the future development of more profound hypothyroidism.
Patients with postpartum thyroiditis with persistently elevated thyroid autoantibody levels have an increased likelihood of permanent hypothyroidism.
In cases of neonatal hypothyroidism, the detection of anti-TPO or anti- Tg autoantibodies in the infant suggests transplacental antibody transfer, particularly if the mother has a history of autoimmune thyroiditis or detectable thyroid autoantibodies. The neonatal hypothyroidism is likely to be transient in these cases.
Thyroid Cancer Follow-Up:
Following therapy of differentiated follicular-cell derived thyroid cancer, all patients who have no, or only trivial, amounts of normal residual thyroid tissue and no persistent or recurrent cancer will have undetectable or very low serum thyroglobulin (Tg) levels. Persistently elevated or rising serum Tg levels, either on or off thyroxine replacement therapy, suggest possible tumor persistence or recurrence. However, if a patient also has measurable anti-Tg autoantibody levels >= 22 IU/mL, the results of serum Tg measurements are unreliable. Anti-Tg autoantibodies may result in both falsely-low and, less commonly, falsely-high serum Tg measurements. Therefore, in anti-Tg-positive patients, serum Tg measurements should either not be used in thyroid cancer follow-up or be interpreted with extreme caution. A thyroglobulin antibody result of <22 IU/mL is unlikely to cause clinically significant thyroglobulin assay interference. It is recommended that the thyroglobulin result be reviewed for concordance with clinical presentation.
Comments:
This assay may be significantly impacted by high-dose biotin
(>5 mg dose) taken within previous 12 hours. High concentrations of
biotin may lead to falsely increased results. These concentrations
may be found in patients taking over-the-counter supplements with
biotin content much higher than nutritional requirements for biotin.
Specimens should not be collected until at least 12 hours after the
last dose.
Useful for an adjunct to anti-thyroid peroxidase (anti-TPO) autoantibody, antithyrotropin-receptor autoantibody, and thyroid- stimulating immunoglobulin measurements in the diagnosis of autoimmune thyroid diseases: Hashimoto disease, postpartum thyroiditis, neonatal hypothyroidism, and Graves disease.
Cautions:
Low titers of thyroid autoantibodies may be observed in the absence of autoimmune or other thyroid diseases and are considered a nonspecific finding. The population prevalence of such nonspecific low-level anti- thyroglobulin (anti-Tg) positivity is higher in females than in males and increases with age in both genders.
Anti-Tg 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 antibody-negative by others. Comparing anti-Tg antibodies values from different methods might lead to erroneous clinical interpretation.
Tg concentrations >2,000 ng/mL may lead to falsely elevated anti-Tg concentrations.
Useful for an adjunct to anti-thyroid peroxidase (anti-TPO) autoantibody, antithyrotropin-receptor autoantibody, and thyroid- stimulating immunoglobulin measurements in the diagnosis of autoimmune thyroid diseases: Hashimoto disease, postpartum thyroiditis, neonatal hypothyroidism, and Graves disease.
Cautions:
Low titers of thyroid autoantibodies may be observed in the absence of autoimmune or other thyroid diseases and are considered a nonspecific finding. The population prevalence of such nonspecific low-level anti- thyroglobulin (anti-Tg) positivity is higher in females than in males and increases with age in both genders.
Anti-Tg 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 antibody-negative by others. Comparing anti-Tg antibodies values from different methods might lead to erroneous clinical interpretation.
Tg concentrations >2,000 ng/mL may lead to falsely elevated anti-Tg concentrations.
Test
Limitations:
Hemolysis: No significant interference up to an H index of 1690
(approximate hemoglobin concentration: 1690 mg/dL).
Lipemia: No significant interference up to an L index of 2000 (approximate triglycerides concentration: 4000 mg/dL). Note there is poor correlation between turbidity and triglyceride concentration.
Icterus: No significant interference up to an I index of 66 (approximate conjugated and unconjugated bilirubin concentration: 66 mg/dL).
Lipemia: No significant interference up to an L index of 2000 (approximate triglycerides concentration: 4000 mg/dL). Note there is poor correlation between turbidity and triglyceride concentration.
Icterus: No significant interference up to an I index of 66 (approximate conjugated and unconjugated bilirubin concentration: 66 mg/dL).
Methodology:
Electrochemiluminescence Immunoassay
Sample
Processing:
Centrifuge at a speed and time necessary to get barrier separation of plasma/serum and cells within 1 hour of collection.
Separate plasma into screw-capped plastic vial.
Do not send primary tube if all plasma has been transferred to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.
Separate plasma into screw-capped plastic vial.
Do not send primary tube if all plasma has been transferred to another tube.
Each sample must be labeled with at least TWO full patient identifiers (First/Last Name & DOB are sufficient for non-UIHC affiliated clients) to avoid sample rejection/delays.
Sample
Storage:
Refrigerate.
Transport
Instructions:
Place labeled specimen into zip-lock type biohazard bag; seal bag.
Place completed requisition into outside pocket of bag.
Transport in cooler with refrigerated coolant packs.
Place completed requisition into outside pocket of bag.
Transport in cooler with refrigerated coolant packs.
CPT Code:
86800
See also:
Thyroglobulin, Tumor Marker (Includes Anti-TG), Serum
Thyroglobulin, Tumor Marker (Includes Anti-TG), Serum
See Additional Information:
Biotin Interference with Immunoassays
Biotin Interference with Immunoassays