Share
PrintTest Details
Turnaround Time
Within 1 day
Use
FTI is a physiologic index of metabolic activity that correlates with free thyroxine (T4)
Special Instructions
This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.
Test Includes
Free thyroxine index; T3 uptake (THBR); thyroxine (T4)
Methodology
Electrochemiluminescence Immunoassay (ECLIA)
Related Documents
For more information, please view the literature below.
Thyroid Cascade Testing: Differential Laboratory Diagnosis of Thyroid Function
Specimen Requirements
Information on collection, storage, and volume
Specimen
Serum (preferred) or plasma
Volume
1 mL
Minimum Volume
0.7 mL (Note: This volume does not allow for repeat testing.)
Container
Red-top tube, gel-barrier tube, or green-top (lithium heparin) tube. Do not use oxalate, EDTA, or citrate plasma.
Storage Instructions
Room temperature
Collection
If a red-top tube or plasma is used, transfer separated serum or plasma to a plastic transport tube.