Thyroxine free, dialysis/mass spectrometry

Alphabetical Test listing

Thyroxine free, dialysis/mass spectrometry-994

Test name:

Test number:

994

Excellian order number:

LAB994

Abbreviation:

MSO

Alternate names:

Free thyroxine T4
T4 free, dialysis/mass spectrometry
Free T4 by equilibrium

Useful for:

Free Thyroxine is used to evaluate thyroid gland function and to diagnose thyroid disease, as well as to monitor effectiveness of thyroid hormone treatment.

Specimen type:

Serum

Collection container:

Gold serum separator (SST) tube

Volume:

1.0 mL

Minimum volume:

0.5 mL
Submission of the minimum volume does not allow for repeat testing

Collection instructions:

Immediatley following collection, mix sample by gently inverting 5 times

Processing instructions:

Allow sample to clot for a minimum of 30 minutes
Spin within 45 minutes of sample collection
Transfer serum to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as serum
Freeze

Transport container:

Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp)

Alternate specimen type:

EDTA plasma

Alternate collection container:

Red serum vial/tube, 5 mL

Lavender (EDTA), 4mL

Alternate collection instructions:

Lavender:

Immediately following collection, mix sample thoroughly by gentle inverting 8 - 10 times, to prevent clotting

Alternate processing instructions:

Red:

Allow sample to clot
Spin within 45 minutes of sample collection
Transfer serum to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as serum
Freeze

Lavender:

Spin within 45 minutes of sample collection
Transfer plasma to a Screw-cap polypropylene frozen transport vial/tube - 4mL (LabCorp), labelled as EDTA plasma
Freeze

Transport and stability:

Frozen (preferred) - 453 days

Refrigerated - 5 days

Ambient - 2 days

Freeze/thaw cycles - stable x3

Performing lab:

Esoterix Endocrinology (500329) via LabCorp (501902): R-NX

Days set up:

Mo - Fr

TAT:

6+11 days

Method:

Direct dialysis mass spectrometry

High pressure liquid chromatography/mass spectrometry (HPLC/MS)

Reference ranges:

Age	Range (ng/dL)
Premature (0-4 wks)	0.86−4.46
Newborn 0–2 wks	0.84−4.97
2 weeks – 12 months	0.81 – 2.12
1 – 11 years	0.65 – 1.9
Pubertal children and adults	0.8 – 1.7
Pregnant female
First trimester (0 – 13.3 wk)	0.65 – 1.4
Second trimester (13.4 – 26.6 wk)	0.5 – 1.3
Third trimester (>26.6 wk)	0.5 – 1.1

CPT codes:

84439

Subject to medical necessity (Y/N):

Yes

LCD/NCD:

Medical necessity

LOINC code:

Result 6892-4

Date created:

05/22/2019

Revised date:

12/20/2023

Review date:

12/20/2023