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Test Code 1806 T4 (Thyroxine), Free

Performing Laboratory

Barnes-Jewish Hospital Laboratory


Cobas ECLIA electrochemiluminescence

Literature References:

Package Insert: Free Thyroxine FT4 II. Roche Corporation 10/2014.

Specimen Requirements

Specimen Type: Plasma
Container/Tube: Mint green top (lithium heparin)
Specimen Volume: Full tube
1 mint green-top (lithium heparin) tube
Additional Information: Specimen drawn from recently heparinized patients may cause spurious results.

Day(s) Test Set Up

Monday through Sunday

Turnaround Time:
STAT: 1 hour after receipt in laboratory 
Routine: 2-4 hours after receipt in laboratory

Reference Values

0.9-1.7 ng/dL

Literature Reference:

Tietz Fundamentals of Clinical Chemistry, 5th Edition, Editors: Burtis CA and Ashwood ER, Chapter 55, p. 1935. W.B. Saunders Company, 2014

Test Classification and CPT Coding


Additional Information

For BJH Laboratory Use Only

Alternate Tube(s):

1 dark green-top (lithium heparin) tube

1 Plain red top

Separator gel tube is acceptable

Analyte Stability:

See Analyte Stability Chart in Special Instructions.

Laboratory Processing Instructions:

Test performed in BJH Core Lab.  Processed by automated line for delivery to the Cobas 8000. Completed specimens are stored refrigerated for 5 days.

Note: Free T4 by equilibrium dialysis (plain, red-top tube) may be obtained as a send out. Laboratory Medicine resident approval is required (314-747-1320). If approved, order #91548 T4, Free, Direct Dialysis and forward to Mayo Medical Laboratories.

Specimen Transport Temperature


Special Instructions

LOINC Code Information

Name LOINC Code
T4, Free 3024-7