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 Thyroid Stimulating Hormone (0070145) 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: 5 days; 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



Compliance Category

FDA

Note
Hotline History
N/A
CPT Codes

84439

Components
Component Test Code* Component Chart Name LOINC
0070138 Thyroxine Free 3024-7
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Free Thyroxine
  • FT4, Serum
  • Non-Protein Bound Tetraiodothyronine
  • T4 Free, Serum
  • T4, Free
  • Thyroid Function Cascade
Thyroxine, Free (Free T4)