THYROXINE FREE, DIRECT DIALYSIS

Specimen Required
Draw blood in a SST. Centrifuge, separate serum from cells within 1 hour and send 1.0 mL serum (0.5 mL minimum) refrigerated in a screw-capped plastic vial.

Rejection Criteria
Lipemia; heparin plasma; EDTA plasma

Methodology
Equilibrium Dialysis, Chromatography/Mass Spectrometry

Stability
Room Temperature: 4 days; Refrigerated: 14 days; Frozen: 35 days

Reference Range
Adult:   0.9-2.2 ng/dL  
Prematures, 25-30 weeks,
   Birth - 7 days:   0.5-3.3 ng/dL  
Prematures, 31-36 weeks,   Birth-7 days:   1.3-4.7 ng/dL  
Cord Blood, >37 weeks:   1.2-2.2 ng/dL  
Birth-4 days:   2.2-5.3 ng/dL  
2 months-2 years:   1.2-2.5 ng/dL  
3-17 years:   1.0-2.4 ng/dL  
Pregnancy:
First Trimester:   0.9-2.0 ng/dL  
Second Trimester:   0.8-1.5 ng/dL  
Third Trimester:   0.8-1.7 ng/dL  

Performed
Monday-Saturday

Turnaround Time5-7 days
Test CodeFT4DD
CPT-4 Code (s)
84439
LOINC Codes
6892-4

Warde
Medical
Laboratory