Thyroxine (T4) Free
Test Code
FRT4
Description
The T4 Free (FT4) test measures serum thyroxine (T4) that is not bound to thyroid hormone-binding proteins (thyroid hormone-binding globulin [TBG], transthyretin, albumin) and is thus readily available to target cells. This test is used with thyroid-stimulating hormone measurement (TSH, test code 899) in the diagnosis of hyperthyroidism (usually displaying elevated FT4) and hypothyroidism (low FT4), including congenital and acquired hypothyroidism.
Collect
Plain red top or SST tube.
Pediatric Collection
Minimum volume: 0.3mL serum
Unacceptable Conditions
Grossly hemolyzed, icteric, and lipemic specimens
Storage Transport Temp
Offsite: Send frozen serum Priority Overnight via FedEx and in a well insulated container on dry ice.
Stability
Stability after cell separation:
24 hours at RT (15-25°C)
6 days refrigerated at 2-8°C
>6 days ≤ -10°C (avoid multiple freeze / thaws)
Performed
Mon-Fri
Methodology
2 Step Competitive with Labeled Antibody Chemiluminescent
Turnaround Time
Results same day if samples are received prior to 6PM
Department
Core Lab
Synonyms
Free T4 (Thyroxine, free, serum);FRT4
Study Offerings
Not offered
Reference Interval
0.6 - 1.1 ng/dL
CPT Code
84439
New York Approved
FDA Approved or Cleared
FDA
Approved or Cleared