T3, Free

Supply #T01 - Red/Gray SST 8.5mL

Test Code: 34429

CPT Code(s): 84481

Methodology: Immunoassay (IA)

Clinical Significance: T3, Free - The T3, Free (FT3) test measures serum triiodothyronine (T3) not bound to thyroid hormone-binding proteins (thyroid hormone-binding globulin [TBG], transthyretin, albumin). It is used, primarily in concert with measurement of thyroid-stimulating hormone (TSH, test code 899) and free T4 (FT4, test code 866), in the diagnosis and management of hyperthyroidism and to clarify thyroid hormone status in the presence of a possible thyroid hormone-binding protein abnormality.

The FT3 (or total T3) test is usually ordered following an abnormally low TSH result and/or a clinical picture suggestive of hyperthyroidism, particularly if the free T4 test (FT4, test code 899) result is not elevated. Up to 10% of patients with proven hyperthyroidism (due to Graves disease or an autonomously secreting thyroid nodule) may have an elevated FT3 but normal FT4 (T3 toxicosis), particularly early in the course of disease or as an early sign of relapse after treatment [1]. In contrast, there is limited utility for FT3 testing for suspected hypothyroidism as FT3 levels may not drop until well after both TSH and FT4 rise [2].

Additional names: Free T3

Collection Guide: 

Supply: T01 - Red/Gray SST 8.5mL

Preferred Specimen Requirements: Serum

Preferred Volume: 1mL

Container Type: Serum Separator tube (SST)

Transport Temperature: Room Temperature

Specimen Stability:
 Room Temperature: 7 days

Reject due:
 Specimens exceeding stability; Unlabeled or improperly labeled specimens; Specimens other than serum

For additional supply or collection device information, please contact DLO's Customer Service at (800) 891-2917, option 2.

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 payor being billed.