This test measures the amount of free thyroxine or Free T4, in the blood. Free T4 is the not bound to a protein but free. Unlike T4 it is not affected by protein levels and protein binding ability. Since free T4 is the active form of thyroxine, it is thought by many to be a more accurate reflection of thyroid hormone function and, in many cases, its use has replaced that of the total T4.
Whichever thyroxine measurement is ordered, it is usually ordered along with or following a TSH test. This helps the doctor to determine whether the thyroid hormone feedback system is functioning as it should, and the results of the tests help to distinguish between different causes of hyper- and hypothyroidism.
Free T4 AccuLite CLIA Kits
Enzyme Immunoassay, Chemiluminescence
Competitive Assay, Antibody-Coated Plate
0, 0.4, 1, 1.85, 3.50, 7.20 ng/dl* (Lot Specific)
May 6, 2016 Notice
T4 ELISA Enzyme and CLIA Tracer packaging updated in all T4, FT4, Thyroid VAST, Free Thyroid VAST, and NT4 Kits from clear to amber vial as a better safeguard against reagent light sensitivity.