Ordering Recommendation

Not preferred for initial thyroid disorder screening; for initial screening, refer to Thyroid Stimulating Hormone (0070145). Order following an abnormal thyroid stimulating hormone (TSH) result to diagnose thyroid disease. In cases of suspected secondary hypothyroidism, order in conjunction with Thyroid Stimulating Hormone (0070145).

New York DOH Approval Status

This test is New York state approved.

Specimen Required

Patient Preparation
Collect

Serum separator tube or plasma separator tube. Also acceptable: Green (lithium heparin), lavender (K2EDTA or K3EDTA ) or pink (K2EDTA).

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

Methodology

Quantitative Electrochemiluminescent Immunoassay

Performed

Sun-Sat

Reported

Within 24 hours

Reference Interval

Effective February 22, 2022

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 0.9-1.7 ng/dL
Pregnancy, 1st Trimester 0.9-1.4 ng/dL
Pregnancy, 2nd Trimester 0.7-1.3 ng/dL

Interpretive Data



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)