Thyroxine Binding Globulin

Cleveland Heartlab T, Test

CPT Code: 84442
Order Code: C2378
ABN Requirement: No
Synonyms: TBG
Specimen: Serum
Volume:  0.5 mL
Minimum Volume:  0.4 mL
Container: Gel-barrier tube (SST, Tiger Top)



  1. Collect and label sample according to standard protocols.
  2. Gently invert tube 5 times immediately after draw. DO NOT SHAKE.
  3. Let tube stand in a vertical position to allow blood to clot 30 minutes.
  4. Centrifuge for 10 minutes.

Transport: Store serum at 2-8°C after collection and ship the same day per packaging instructions provided with the Cleveland HeartLab shipping box.


Ambient (15-25°C): 24 hours
Refrigerated (2-8°C):
7 days
Frozen (-20°C):
30 days
Deep Frozen (-70°C):
30 days

Causes for Rejection: Specimens other than serum; improper labeling; samples not stored properly; samples older than stability limits

Methodology: Chemiluminescence Immunoassay (CLIA)

Turn Around Time: 3-6 days

Reference Range:

Age ug/mL
All Ages 13-30


Clinical Information: Determine binding capacity for T4; document cases of hereditary deficiency of TBG, in work-up of thyroid disease, particularly in patients with low T4, high T3 (uptake) who clinically seem eumetabolic. Such patients may have hereditary anomalies of TBG. They may require no treatment.

The CPT codes provided 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 payer being billed.