Thyroxine, Free (Free T4)
0070138
 
Ordering Recommendation
Not the preferred initial thyroid disorder screening test. Order following an abnormal thyroid stimulating hormone (TSH) result to diagnose thyroid disease. Order in conjunction with TSH in cases of suspected secondary hypothyroidism.
Mnemonic
FT4
Methodology
Quantitative Electrochemiluminescent Immunoassay
Performed
Sun-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 (sodium or lithium heparin) or lavender (EDTA).  
Specimen Preparation
Allow specimen to clot completely at room temperature. Separate serum or plasma from cells ASAP or within 2 hours of collection. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.5 mL)  
Storage/Transport Temperature
Refrigerated.  
Unacceptable Conditions
Grossly hemolyzed specimens.  
Remarks
 
Stability
After separation of cells: Ambient: 24 hours; Refrigerated: 1 week; Frozen: 1 month  
Reference Interval
Effective May 16, 2011
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 0.5-​2.3 ng/dL
2-​6 years 0.9-​1.8 ng/dL
7-​11 years 0.9-​1.7 ng/dL
12-​19 years 0.9-​1.6 ng/dL
20 years and older 0.8-​1.7 ng/dL
Pregnancy, 1st Trimester 0.9-​1.4 ng/dL
Pregnancy, 2nd Trimester 0.7-​1.3 ng/dL
Interpretive Data
Note
CPT Code(s)
84439
Components
Component Test Code*Component Chart Name
0070138Thyroxine Free
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, contact interface support at interface.support@aruplab.com.
Cross References
  • Free Thyroxine
  • FT4, Serum
  • Non-Protein Bound Tetraiodothyronine
  • T4 Free, Serum
  • T4, Free
  • Thyroid Function Cascade