THYROXINE, FREE

Test Code

FT4 (OE & LAB)

Alias/See Also

FT4, Free Thyroxine, Thyroid, Free T4

CPT Codes
84439

Preferred Specimen

Gold Tube (SST)

Patient Preparation
Note: This test is sensitive to Biotin and result may be falsely elevated in patinets taking high doses.

Minimum Volume

0.5mL (1mL optimal)

Other Acceptable Specimens

Green Tube (Lithium Heparin)

Instructions

Centrifuge for separation of serum or plasma and red cells within 2 hours.

Transport Container

GOLD Tube

Transport Temperature

Room Temperature

Specimen Stability

2-8°C up to 7 days

15-30°C up to 8 hours

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

Quantity not sufficient (QNS)

Methodology
Chemiluminescent Immunoassay (CIA)

Setup Schedule

DAILY, as received

Report Available

STAT: <60 minutes
Routine: <4 hours

Reference Range

Male/Female All Ages: Normal Range: 0.58-1.64 ng/dL
Reference ranges may vary based on performing lab. Use lab reports when interpreting patient results.

Clinical Significance

FT4 aids in the diagnosis of hyper/hypothyroidism. In conjunction with TSH, it can help determine if the feedback loop is intact.

Performing Laboratory
Mount Sinai Hospital
Holy Cross Hospital

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.