T 4 Free, Direct Dialysis

Test Code

T4FDD

Alias/See Also

LAB13031

CPT Codes
84439

Preferred Specimen

2 mL serum

Patient Preparation
Fasting preferred

Minimum Volume

0.5 mL

Instructions

Please specify the patient's age on the request form

Transport Container

Gold Serum Separator Tube

Transport Temperature

Refrigerated

Specimen Stability

Room temperature: 7 days Refrigerated: 7 days Frozen: 28
days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Lipemia • Heparin plasma • EDTA plasma

Methodology

Direct Equilibrium Dialysis • Immunoassay (IA)

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

Daily a.m.

Report Available

Next day

Reference Range

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 Weeks-2 Years 0.8-2.0 ng/dL

3-20 Years 1.0-2.4 ng/dL

21-87 Years 0.8-2.7 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

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

Last Updated: February 17, 2023

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.