Test Code FT4BD / 501902-EX THYROXINE, FREE (FT4) BY DIALYSIS/MASS SPECTROMETRY

Important Note

This test should be ordered ONLY by an endocrinology specialist or as a result of consultation with an endocrinology specialist. For all other patients, please order test code T4F.

Additional Codes

Software	Test Code
Label Text	FT4BD
EPIC	LAB20291
LabCorp (Esoterix)	501902

Performing Laboratory

Esoterix Laboratory Services (LabCorp Specialty Testing Group)

Clinical Significance

Used where abnormal binding proteins are known to exist.

Useful For

Determining thyroid status of sick, hospitalized patients. Useful in pediatric populations.

Method Name

Direct dialysis mass spectrometry; high-pressure liquid chromatography/mass spectrometry (HPLC/MS)

Reference Values

1 – 11 Years: 0.65 – 1.9

Pubertal Children and Adults:

Males: 0.8 – 1.7

Females: 0.8 – 1.7

Pregnant Females:

1st Trimester (0-13.3 wks): 0.65 – 1.4

2nd Trimester (13.4-26.6 wks): 0.5 – 1.3

3rd Trimester (>26.6 wks): 0.5 – 1.1

Days and Times Test Performed

Monday through Friday

Report Available

6 - 11 Days

Analytic time for send out tests is the time it will take to perform testing once it has arrived at the performing reference lab. Please add 1 to 2 days from time of collection to allow for receipt at NorDx central lab and shipment of specimen, add another day if specimen is collected on the day before a weekend or holiday.

Specimen Type

Serum Preferred : Red-top tube or SST (gel-barrier tube)

Plasma: Lavender-top (EDTA) tube

Preferred Container

Red Top Tube

Preferred Volume

Serum: 1 mL (Red Top Tube) – Min volume does not allow for repeat testing.

Minimum Volume

Serum: 0.5 mL (Red Top Tube)

Specimen Collection and Handling

Spin specimen within 45 minutes of collection, separate serum or plasma from clot/cells and send frozen aliquot in a plastic, screw-capped vial.

PLEASE NOTE: To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Specimen Stability Information

Specimen Type: Serum and Plasma

Refrigerated: 5 Days

Room Temp: 2 Days

Note: Max stability: 453 days FROZEN (-20°C). Stable x3 freeze/thaw cycles.

Add On Capable

Yes

CPT Code Information

CPT Code	CPT Description	CPT Disclaimer
84439	Thyroxine, Free, Quantitative

Performing Laboratory Location