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Thyroglobulin, Ultrasensitive (Tumor Marker; includes anti-Tg Ab testing)

Item Value
Test Update Information Test introduced effective March 19, 2013. All orders for thyroglobulin testing starting March 19, 2013 are performed using this highly sensitive assay.

Anti-thyroglobulin antibody reference range changed effective July 1, 2014.
Approval req'd? Yes
Available Stat? No
Test code TGA
Test group Thyroid tests
Performed by Parnassus Chemistry (for Thyroglobulin)
China Basin Chemistry (for Thyroglobulin Ab)
In House Availability Tuesday, Friday (day shift)
Method Immunoenzymatic assay - Beckman Access assay on Unicel DxI 600 (for Thyroglobulin)

Chemiluminescent Microparticle Immunoassay - Abbott Architect i2000 (for Thyroglobulin Ab)
Container type Red top or Gold top
Amount to Collect 3 mL blood
Sample type Serum
Preferred volume 1.1 mL serum
Min. Volume 1.0 mL serum
Processing notes Refrigerate serum.
Units
Thyroglobulin Ab screen IU/mL
Thyroglobulin µg/L
Normal range Thyroglobulin:
Male 1.4-29.2 µg/L
Female 1.5-38.5 µg/L


Thyroglobulin Ab* < 2.00 IU/mL


*Reference range is based on the functional CV cutoff (20% CV cutoff) for the assay estimated by monitoring the CV in low end patient pools and samples tested over periods of 1 - 6 months. This functional CV cutoff is in accord with that reported by Pickett et al, Ann Clin Biochem, 49:463-467, 2012 for the Abbott Architect assay. Approximately 80% of healthy subjects with normal thyroid function tests and no thyroperoxidase antibodies will have an anti-TG antibody level < 2.00 IU/mL in this assay. The normal range cutoff has been set at the lower reporting limit of the assay (functional CV cutoff) in accordance with the view that any detectable level of anti-thyroglobulin antibody may be considered abnormal and might negatively interfere in the thyroglobulin assay
Synonyms Tg; TGLB
Stability Refrigerated 1 week frozen -20C 1 month
Turn around times 1-5 days
Additional information Samples tested for thyroglobulin will automatically be screened for the presence of thyroglobulin antibodies using a sensitive assay for anti-thyroglobulin antibodies (see TGLB Antibodies, test code TGAB). The presence of anti-thyroglobulin antibodies can interfere in this thyroglobulin assay and may cause falsely decreased results.

Note: Assays for anti-thyroglobulin antibodies are not well standardized and results with this Abbott Architect assay should not be directly compared with the results of other anti-thyroglobulin antibody assays.

The Architect anti-thyroglobulin assay is more sensitive for detection of anti-TG antibodies than other commonly used anti-TG antibody assays including the Siemens Immulite assay when using cutoffs based on the manufacturer's reference range or functional CV cutoff in some cases (Pickett et al. Annals of Clinical Biochemistry 49:463-467, 2012). The coefficient of variation of this assay is approximately 20% at a level of 2.00 IU/mL and approximately 6% at a level of 4.11 IU/mL. Results below the functional CV cutoff of 2.00 (20% CV cutoff) are reported as <2.00.

Thyroglobulin results obtained with this assay should not be compared to results generated with other thyroglobulin assays owing to differences in assay design and calibration. In this Beckman Access assay on the Unicel Dxi platform, the functional sensitivity defined as the lowest value that can be measured in thyroglobulin-negative antibody serum with a 20% coefficient of variation has been verified in house and in other laboratories to be < 0.1 µg/L (Malandrino et al, J Clin Endocrinol Metab 2011). Results below 0.1 µg/L are reported as < 0.1 µg/L

Thyroglobulin levels are useful to assess the presence of residual differentiated thyroid carcinoma. Athyrotic individuals should have extremely low to undetectable levels of thyroglobulin. Increasing levels indicate possible recurrence or metastasis. Levels are not elevated in medullary or anaplastic thyroid carcinomas nor with small tumors, and are generally not useful as a routine screening test for thyroid cancer.

Normal reference ranges were adopted from the literature and verified in house by measuring thyroglobulin in serum from 138 healthy blood donors with normal TSH levels and negative for anti-thyroglobulin antibodies and anti-TPO antibodies (Giovanella et al. Clin Chem Lab Med, 2011).
CPT coding Thyroglobulin Ab Screen 86800-90
Thyroglobulin , Tumor Marker 84432-90
LOINC code 8098-6
Last Updated 7/1/2014 8:26:02 AM
Entry Number 1282
Lab Procedure Link Click here for Procedure
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