T4 Free, Direct Dialysis and T4, Total

Test Code

CPT Codes
84436, 84439

Preferred Specimen
2 mL serum

Patient Preparation
Fasting preferred

Minimum Volume
1 mL

Please specify on the request form the patients age.

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 4 days
Refrigerated: 7 days
Frozen: 28 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Lipemia • Heparin plasma • EDTA plasma

Equilibrium Dialysis • Chromatography/Mass Spectrometry • Chemiluminescence (CL)

Setup Schedule
Set up: Mon-Sat; Report available: 3-4 days

Reference Range
T4, Free Direct Dialysis
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 Years-17 Years 1.0-2.4 ng/dL
  First Trimester 0.9-2.0 ng/dL
  Second Trimester 0.8-1.5 ng/dL
  Third Trimester 0.8-1.7 ng/dL

T4, Total
<1 Month Not established
1-23 Months 6.0-13.2 mcg/dL
2-12 Years 5.5-12.1 mcg/dL
13-20 Years 5.5-11.1 mcg/dL
>20 Years 4.8-10.4 mcg/dL
  First Trimester 6.4-15.2 mcg/dL
  Second Trimester 7.4-15.2 mcg/dL
  Third Trimester 7.7-13.8 mcg/dL
  All TrimestersTogether 7.0-14.7 mcg/dL

Clinical Significance
For the differential diagnosis of euthyroid hyperthyroxinemia from hyperthyroidism or for the differential diagnosis of euthyroid hypothyroxinemia from hypothyroidism.

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.