ARUP's Laboratory Test Directory

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

Mnemonic: FT4 ED-TMS

Ordering Recommendation: Not recommended for routine evaluation of thyroid disorders. Order Thyroxine, Free (Free FT4) (0070138), instead.
Methodology: Quantitative Equilibrium Dialysis/High Performance Liquid Chromatography-Tandem Mass Spectrometry
Performed: Mon-Fri
Reported: 2-5 days
Specimen Required: Collect: Plain red.

Specimen Preparation: Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 0.3 mL)

Storage/Transport Temperature: Refrigerated.

Stability (collection to initiation of testing): 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:

See Compliance Statement B: www.aruplab.com/CS
CPT Code(s): 84439
Cross References: Direct Dialysis (Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry), FT4 (Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry), T4, Free, Equilibrium Dialysis (Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry)