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Thyroxine, Free (Free T4)
Ordering Recommendation
The preferred alternative to this test is Thyroxine, Free (Free T4)
Methodology
Quantitative Electrochemiluminescent Immunoassay (ECLIA)
Performed
Mon-Sat
Reported
Within 24 hours
New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation:
Collect:
Serum separator tube or plasma separator tube. Also acceptable: Green (lithium heparin), lavender
Specimen Preparation:
Allow specimen to clot completely at room temperature. Separate serum or plasma from cells ASAP or within 2 hours of collection.
Storage/Transport Temperature:
Refrigerated.
Unacceptable Conditions:
Grossly hemolyzed specimens.
Remarks:
Stability:
After separation of cells: Ambient: 8 days; Refrigerated: 2 weeks; Frozen: 2 years
Reference Interval
Free Thyroxine, ng/dL
0-3 days
0.7-2.7 ng/dL
4-30 days
0.8-3.1 ng/dL
1-23 months
2-6 years
0.5-2.3 ng/dL
0.9-1.8 ng/dL
7-11 years
0.9-1.7 ng/dL
12-19 years
12-19 years
0.9-1.6 ng/dL
0.9-1.6 ng/dL
20 years and older
0.9-1.7 ng/dL
Pregnancy, 1st Trimester
0.9-1.4 ng/dL
Pregnancy, 2nd Trimester
0.7-1.3 ng/dL
Interpretive Data
Thyroxine, Free (Free T4) is the preferred test alternative for T Uptake and Free Thyroxine Index tests.
Note
CPT Code
84439
Components
Component Test Code
Component Chart Name
LOINC
0070138
Thyroxine Free
3024-7
Aliases
Free Thyroxine
FT4, Serum
Non-Protein Bound Tetraiodothyronine
T4 Free, Serum
T4, Free
Thyroid Function Cascade
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