T4 Free, Direct Dialysis

Test Code

CPT Codes

Preferred Specimen
1 mL serum

Patient Preparation
Fasting preferred

Minimum Volume
0.5 mL

Please specify the patient's age on the request form

Transport Temperature
Room temperature

Specimen Stability
Room temperature: 4 days
Refrigerated: 14 days
Frozen: 35 days

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


Equilibrium Dialysis • Chromatography/Mass Spectrometry

FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by FDA. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

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

Reference Range
Adult0.9-2.2 ng/dL
Prematures, 25-30 Weeks
  Birth-7 Days0.5-3.3 ng/dL
Prematures, 31-36 Weeks
  Birth-7 Days1.3-4.7 ng/dL
Cord Blood, >37 Weeks1.2-2.2 ng/dL
Birth-4 Days2.2-5.3 ng/dL
2 Months-2 Years1.2-2.5 ng/dL
3 Years-17 Years1.0-2.4 ng/dL
  First Trimester0.9-2.0 ng/dL
  Second Trimester0.8-1.5 ng/dL
  Third Trimester0.8-1.7 ng/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.