Triiodothyronine - Free (T-3)
Label Mnemonic: FT3
Epic Lab Code: LAB137
Downtime Form: A-1a Miscellaneous Request
6240 RCP
Collection Medium:
Plasma Separator Tube 4.5 mL
Alternate Collection Media:
Call laboratory for additional acceptable specimen collection containers.
3 mL whole blood in light green top or TWO Microtainer® devices
Testing Schedule:
24 hrs/day, 7 days a week, including holidays.
Turn Around Time:
1 hour (upon receipt in laboratory)
Reference Range:
Less than 1 month: 1.4-5.5 pg/mL Less than 1 year: 2-6.9 pg/mL 1 - 5 years: 2.4-6.7 pg/mL 5 - 18 years: 2.3-5.5 pg/mL Adults: 2.57-4.43 pg/mL To convert results to ng/dL, multiply result x.1 To convert results to pmol/L, multiply result x 1.54
Test Limitations:
The assay is unaffected by icterus (bilirubin is less than 66 mg/dL), hemolysis (Hb is less than 1000 mg/dL), lipemia (Intralipid is less than 2000 mg/dL) and biotin is less than 100 ng/mL (criterion: recovery within plus or minus 10% of initial value). In patients receiving therapy with high biotin doses (i.e. is greater than 5 mg/day) no sample should be taken until at least 8 hours after the last biotin administration. 18 commonly used pharmaceuticals were tested in vitro. No interference with the assay was found. Therapeutic concentrations of acetylsalicylic acid and furosemide lead to elevated FT3 values. Autoantibodies to thyroid hormones can interfere with the assay. The risk of interference from potential immunological interactions between test components and rare sera has been minimized by the inclusion of suitable additives. In rare cases, interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur. FT3 contains additives which minimize these effects. For diagnostic purposes, the FT3 findings should always be assessed in conjunction with the patient's medical history, clinical examination and other findings.
Electrochemiluminescence Immunoassay
CPT Code: