Ordering Recommendation

Not recommended for routine evaluation of thyroid disorders. Preferred test is Thyroxine, Free (Free FT4) (0070138).

Mnemonic
FT4 ED-TMS
Methodology

Quantitative Equilibrium Dialysis/High Performance Liquid Chromatography-Tandem Mass Spectrometry

Performed

Sun, Tue, Thu

Reported

2-5 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Plain Red or Serum Separator Tube (SST).

Specimen Preparation

Separate from cells or gel ASAP or within 2 hours of collection.  Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 0.3 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Plasma.

Remarks
Stability

After separation from cells: Ambient: 4 days; Refrigerated: 2 weeks; Frozen: 1 month

Reference Interval

Effective May 16, 2011

Free Thyroxine ng/dL
Age Female Male
25-30 weeks gestation 0.5-3.3 ng/dL 0.5-3.3 ng/dL
31-36 weeks gestation 1.3-4.7 ng/dL 1.3-4.7 ng/dL
Birth to 1 week 2.2-5.3 ng/dL 2.2-5.3 ng/dL
2-3 weeks 0.9-4.0 ng/dL 0.9-4.0 ng/dL
1-5 months 1.1-2.2 ng/dL 1.1-2.2 ng/dL
6 months-6 years 1.4-2.7 ng/dL 1.4-2.7 ng/dL
7 years-17 years 1.1-2.0 ng/dL 1.1-2.0 ng/dL
18 years and older 1.1-2.4 ng/dL 1.1-2.4 ng/dL
Pregnancy, 1st Trimester 0.7-2.0 ng/dL
Pregnancy, 2nd Trimester 0.7-2.1 ng/dL
Pregnancy, 3rd Trimester 0.5-1.6 ng/dL

Interpretive Data



Compliance Category

Laboratory Developed Test (LDT)

Note
Hotline History
N/A
CPT Codes

84439

Components
Component Test Code* Component Chart Name LOINC
0093244 Free T4 by Equil Dialysis-TMS 6892-4
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Direct Dialysis
  • FT4
  • T4, Free, Equilibrium Dialysis
Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry