Free T3

Test Code

FT3

Alias/See Also

Free Triiodothyronine

CPT Codes
84481

Preferred Specimen

Serum (gold top) tube

Minimum Volume

0.5 mL

Other Acceptable Specimens

Lithium Heparin Plasma (green top) tube

Transport Container

Serum (gold top) tube or Lithium Heparin Plasma (green top) tube

Transport Temperature

Room Temperature or Refrigerated

Specimen Stability

Room Temperature - 1 day; Refrigerated - 7 days

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

Turbidity, Quantity Not Sufficient, IV Contamination

Methodology
Chemiluminescence

Setup Schedule

Daily upon receipt

Report Available

Upon completion of analysis

Reference Range

2.77 - 5.27 pg/mL

Clinical Significance

The free fraction of the circulating triiodothyronine (T3) is considered to exert the main influence on metabolic control. In hyperthyroidism, FT3 concentrations are generally elevated and give efficient discrimination at the euthyroid/toxic borderline, providing an effective method for confirming hyperthyroidism and monitoring of its treatment. In hypothyroidism, FT3 concentrations tend to be lower, but the decrease is insufficient to give clear diagnostic information. FT3 concentrations are independent of the concentration of thyroid hormone-binding proteins, and may be measured in patients with elevated or reduced binding protein concentrations without the need for additional tests of binding capacity. FT3 determinations should be used as part of a thyroid test strategy, which may include free T4 and high sensitivity TSH tests.

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.