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Labcorp Oklahoma, Inc.
Test Directory


Index:

Thyroxine (T4), Free

Order Name FREE T4
Test Number: 4502550
Revision Date 08/12/2020
Test Name Methodology LOINC Code
Thyroxine (T4), Free
Chemiluminescence Assay 3024-7 
SPECIMEN REQUIREMENTS
Specimen Specimen Volume (min) Specimen Type Specimen Container Transport Environment
Preferred 1 mL (0.5) Serum Clot Activator SST Refrigerated
Alternate 1 1 mL (0.5) Plasma Lithium Heparin PST (Light Green Top) Refrigerated
Instructions Stability: Ambient 1 day. Refrigerated 6 days. Frozen > 6 days
GENERAL INFORMATION
Testing Schedule Mon - Fri 
Expected TAT 1-3 days  
Clinical Use The FT4 value combined with the TSH value, gives a more accurate picture of the thyroid status in patients with abnormal TBG levels such as those who are pregnant or those who are receiving treatment with estrogens, androgens, phenytoin or salicylates. 
CPT Code(s) 84439
Lab Section Chemistry