Synonyms: Free Thyroxine; Free T4; Thyroxine
Computer Code: FT4
Specimen Collection: 3 mL blood (light green top (Li Heparin) preferred. Red/gold acceptable). 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, 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.
Minimum Volume: 1 mL
Handling Instructions for Offsite Areas: If red or gold top, allow to clot, centrifuge for 20 minutes, refrigerate. Serum must be removed from red top tube. Min 0.5 mL serum/plasma.
Reference Values: Greater than 1 year old: 0.60-1.30NG/DL. Less than 1 year old: No range established for this age population. Contact the Lab Director at x23501 for consultation.
Lab Code: Chemistry
Requisition: SPEC C
Test Frequency: Daily
Routine TAT: 4 hrs
Stat TAT: 60 min
CPT Code(s): 84439
Methodology Used:
See Addendum XVII