T3, Free

Test Code

T3FRE

Alias/See Also

Epic: LAB137

Free T3
FT3
Free Triiodothyronine

Preferred Specimen

Specimen Type: Serum
Collection Container: Serum gel
Specimen Volume: 3 mL

Minimum Volume

0.3 mL

Other Acceptable Specimens

Specimen Type: Plasma
Collection Container: Green top (Lithium heparin)

Instructions

Centrifuge and separate cells after clot formation and within 4 hours of collection. Remove serum if testing will be delayed more than 24 hours.

Transport Container

Plastic vial

Specimen Stability

Room temperature: Unacceptable
Refrigerated (on gel): 24 hours
Refrigerated (off gel): 6 days
Frozen: >6 days

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

Samples stored on gel >24 hours, unlabeled, mislabeled, wrong tube type, hemolyzed, QNS, exceeds specimen stability requirements.

Methodology

Chemiluminescent microparticle immunoassay (CMIA)

Setup Schedule

Daily

Report Available

Same day

Limitations

For diagnostic purposes, results should be used in conjunction with other data: symptoms, results of other thyroid tests, clinical impressions, etc.
The ARCHITECT Free T3 assay is designed to have a mean potential interference from hemoglobin, bilirubin, triglycerides, and protein of <10% at :
Hemoglobin ≤ 500 mg/dL
Bilirubin ≤20 mg/dL
Triglycerides ≤ 2000 mg/dL
Protein ≤ 12 g/dL

Reference Range

1.71 pg/mL - 3.71 pg/mL

Clinical Significance

Triiodothyronine (T3) is a thyroid hormone with a half-life in serum of 1.5 days. T3 circulates in the blood as an equilibrium mixture of free and protein bound hormone. T3 is bound to thyroxine binding globulin (TGB), prealbumin and albumin. The binding of T3 by these proteins is such that only 0.2 – 0.4% of the total T3 is present in solution as unbound or free T3. This free T3 fraction represents the physiologically biologically active hormone.

Performing Laboratory

Inova Laboratories

2832 Juniper Street

Fairfax, VA 22031

Last Updated: March 9, 2023
Last Review: N. Wolford, March 9, 2023

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.