0093244
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Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry

FT4 ED-TMS
Example Reports
High
Normal

Ordering Recommendation

Not recommended for routine evaluation of thyroid disorders; preferred test is Thyroxine, Free (Free T4) (0070138). Useful to evaluate free thyroxine (FT4) status in individuals with protein-binding abnormalities. Some medications may induce transient changes in FT4 concentrations. This test is not recommended for patients currently receiving heparin treatment because FT4 concentrations may be falsely elevated.

New York DOH Approval Status

This test is New York state 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

Methodology

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

Performed

Sun-Sat

Reported

2-6 days

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

Some medications may induce transient changes in FT4 concentrations. This test  is not recommended for patients currently on heparin treatment as FT4 concentrations may be falsely elevated.

Compliance Category

Laboratory Developed Test (LDT)

Note

Hotline History

View Hotline History

 

Hotline History

Date of Change
Test Name Change
Methodology
Performance/Reported Schedule
Specimen Requirements
Reference Interval
Interpretive Data
Note
CPT Code
Component Change
Other Interface Change
New Test
Inactive
11/13/2023
X
X
X
X
N/A

CPT Codes

84439

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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