TBG (Thyroxine Binding Globulin) (TBG)

Test Code
LAB128

Quest Code
870

Alias/See Also
TBG

CPT Codes
84442

Preferred Specimen
1 mL serum in gold top tube

Minimum Volume
0.5 mL

Other Acceptable Specimens
Plain red top tube

Transport Container
Transport tube

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 7 days
Refrigerated: 7 days
Frozen: 28 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Gross hemolysis

Methodology
Chemiluminescence (CL)

Setup Schedule
Tuesday-friday: PM saturday: AM Tuesday-saturday

Report Available
2 days

Reference Range
Adult Male 12.7-25.1 ug/mL
Adult Female 13.5-30.9 ug/mL
Pediatric
3-8 Years 16.1-24.2 ug/mL
9-13 Years 12.5-25.8 ug/mL
14-17 Years 9.8-23.7 ug/mL

Clinical Significance
Thyroxine-binding globulin (TBG), a glycoprotein produced in the liver, binds both thyroxine (T4) and triiodothyronine (T3) with high affinity. Because TBG accounts for 76% of plasma protein thyroxine-binding activity, an increase or decrease in its circulating level alters total concentrations of T4 and T3 in blood, leading to potential confusion with true thyroid gland dysfunction. A number of diseases and medications, as well as inherited alterations in TBG gene expression, can change the serum TBG concentration. Measurement of TBG is useful in distinguishing quantitative TBG derangements from thyroid dysfunction. This analyte is elevated with estrogen therapy (especially oral contraceptive agents), during pregnancy and or hepatitis. Serum TBG may be decreased in cirrhosis, in the nephritic syndrome and by androgens.

Performing Laboratory
Quest Diagnostics Nichols Institute-Chantilly VA
14225 Newbrook Drive
Chantilly, VA 20151-2228




The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.