T3 Free

Tube Type

Free T3

Test ID

LAB137

EPIC Order

T3, FREE

CPT Code(s)

84481

Group/Individual Test

Individual

Laboratory

Core Laboratory

Tube Station

30

Specimen

Routine:

4 mL blood/Li Heparin plasma separator tube/Mint Green top. Also acceptable serum (Gold SST / Red Top Tube)

Micro:

0.9 mL blood/mint green top bullet/gold top/red top

Stability

Unspun: 4 hours

Spun/separated, Room Temperature: <8 hrs recommended

Spun/separated, Refrigerator: 48 hours

Spun/separated, Frozen: 30 days

Availability

Routine:

24 hrs/7 days

STAT:

Yes

Turnaround Time

2 hrs

Reference Range and
Interpretation

Age Group (years)	Free T3 Reference range (pg/mL) (effective 7/13/2021)
0-1 month	undefined
1-23 months	3.30-5.20
23 months-12 years	3.30-4.80
12-20 years	3.0-4.70
20 years +	2.30-4.20

Comments

Thyroid hormone autoantibodies in serum samples may cause interference in free-hormone immunoassays. Heterophilic antibodies may cause test interference.

Testing is performed using Siemens Atellica FT3 Assay. Performance of this assay has not been established with neonatal specimens.

Reviewed by Travis Sapp on December 26, 2023

UNC Hospitals
McLendon Clinical Laboratories
101 Manning Drive
Chapel Hill, NC 27514