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Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry
Ordering Recommendation
Not recommended for routine evaluation of thyroid disorders. Preferred test is Thyroxine, Free (Free FT4) (0070138).
Methodology
Quantitative Equilibrium Dialysis/High Performance Liquid Chromatography-Tandem Mass Spectrometry
Performed
Sun, Tue, Thu
Reported
2-5 days
New York DOH Approval Status
Specimen Required
Plain Red or Serum Separator Tube (SST).
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)
Refrigerated.
Plasma.
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
This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.
Laboratory Developed Test (LDT)
Note
Hotline History
CPT Codes
84439
Components
| Component Test Code* | Component Chart Name | LOINC |
|---|---|---|
| 0093244 | Free T4 by Equil Dialysis-TMS | 6892-4 |
Aliases
- Direct Dialysis
- FT4
- T4, Free, Equilibrium Dialysis
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