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.
Quantitative Electrochemiluminescent Immunoassay
Within 24 hours
Serum separator tube or plasma separator tube. Also acceptable: Green (sodium or lithium heparin) or lavender (EDTA).
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)
Grossly hemolyzed specimens.
After separation of cells: Ambient: 5 days; Refrigerated: 1 week; Frozen: 1 month
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|
No compliance statements are in use for this test.
|Component Test Code*||Component Chart Name||LOINC|
- Free Thyroxine
- FT4, Serum
- Non-Protein Bound Tetraiodothyronine
- T4 Free, Serum
- T4, Free
- Thyroid Function Cascade