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Test Code FFT4F T4, Free, Direct Dialysis

Additional Codes

Epic Ordering Code LAB3041463
NBS code LBC13326
Service code 36874


Specimen Required


Patient Preparation:

Fasting: 8-16 hours, preferred but not required

Collection Container/Tube:

Preferred: Red top

Acceptable: Serum gel

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL

Collections Instructions:

1. Centrifuge and aliquot 1 mL of serum into a plastic vial.

2. Send refrigerated.


National University Hospital-Singapore Note:

NUH Outreach Laboratories:
Specimen Requirements
Submit only one of the following:
Preferred: Red Top
Acceptable: Yellow Top
Fasting: 8-16 hours, preferred but not required
Processing Requirements
Centrifuge and aliquot serum into a Mayo plastic tube.
Specimen type: Serum
Volume: 1 mL
Storage/transport requirements: Refrigerated

Secondary ID

91548

Method Name

Equilibrium Dialysis, Chromatography/Mass Spectrometry

Reporting Name

T4, Free, Direct Dialysis

Specimen Type

Serum

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 14 days
  Frozen  35 days
  Ambient  4 days

Reject Due To

Lipemia Reject
Heparin plasma Reject
EDTA plasma Reject

Reference Values

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 to 2 years: 1.2-2.5 ng/dL

3 to 17 years: 1.0-2.4 ng/dL

Adult: 0.9-2.2 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

Day(s) Performed

Monday through Saturday

Report Available

4 to 8 days
National University Hospital-Singapore Note:

Please note that this is a referral test requiring transport to the external testing facility and an additional 3-5 days is required.

Performing Laboratory

Quest Diagnostics Nichols Institute

Test Classification

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

CPT Code Information

84439

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FFT4F T4, Free, Direct Dialysis 6892-4

 

Result ID Test Result Name Result LOINC Value
Z1571 T4, Free, Direct Dialysis 6892-4

Useful For

Differential diagnosis of euthyroid hyperthyroxinemia from hyperthyroidism or hypothyroidism

National University Hospital-Singapore Additional Information:

Last updated 06/08/2026