T4 Free, Direct Dialysis

Direct Free T4, Free Thyroxine, Free T4 by Equilibrium Dialysis, FT4 Direct Dialysis, Thyroxine, Free by Direct Dialysis, Free T4 Direct Dialysis, T4 (Thyroxine) Free by Dialysis, Serum

Test Codes

EPIC: LAB1232161, Beaker: T4 Free Dial, Quest: 35167

Department

Send Outs

Instructions

This test is only available to Endocrinologists and Nuclear Medicine Physicians.

Specimen Collection Criteria

Collect (preferred specimen): One Gold-top SST tube.

Also acceptable: One Red-top tube.

Physician Office/Draw Specimen Preparation

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Preparation for Courier Transport

Transport: 1.0 mL serum, at room temperature (20-26°C or 68-78.8°F). (Minimum: 0.5 mL)

Rejection Criteria

• Lipemia.
• Heparin Plasma.
• EDTA plasma.
• Specimens not collected and processed as indicated.

In-Lab Processing

Let specimen clot 30-60 minutes then centrifuge to separate serum from cells. Transfer serum to plastic transport tube and maintain at room temperature (20-26°C or 68-78.8°F) prior to transport.

Transport: 1.0 mL serum, at room temperature (20-26°C or 68-78.8°F). (Minimum: 0.5 mL)

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): 4 days
Refrigerated (2-8°C or 36-46°F): 14 days
Frozen (-20°C/-4°F or below): 35 days

Specimen Storage in Department Prior to Disposal:

Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Laboratory

Sent to Quest Diagnostics, Wood Dale, IL.

Performed

Monday – Saturday.
Results available in 2-4 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 Years-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

Test Methodology

Equilibrium Dialysis, Chromatography / Mass Spectrometry

Interpretation

By Report.

CPT Codes

84439

Contacts

Last Updated

12/17/2025