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Test Name:
T3, Free
- SBMF No:
30016 - Performance Lab Name:
Automated Lab - Test Mnemonic:
T3 FREE - ABN:
Not required - CPT Code:
84481 - LOINC Code:
3051-0 - Also Known As:
Free T3
Free Triiodothyronine
FT3
Triiodothyronine, Free - Spec Type:
Serum - Spec Container:
Gold top (SST) or red top (serum) tube - Alt Spec Type:
Plasma - Alt Spec Container:
Lavender top (EDTA) tube or green top (lithium heparin) tube - Pref Vol:
1.0 mL - Min Vol:
0.4 mL - Fasting:
No - Spec Collect:
Routine venipuncture - Spec Process:
Serum sample tubes, clot 30 minutes
Promptly centrifuge 15 minutes
Immediately transfer serum or plasma to separate plastic tube
Properly centrifuged gel barrier tube sample does not require transfer of serum to separate tube - Spec Store Transport:
Refrigerated - Spec Stability:
1 week refrigerated (2-8°C)
1 month frozen (-20°C) – Do not use frost-free units that undergo repeated freeze/thaw cycles - Spec Reject:
Heat-inactivated sample - Methodology:
Chemiluminescent Immunoassay (CLIA) - Use:
Measuring T3 is useful when altered concentrations of total T3 occur due to changes in T3 binding proteins, especially thyroxine-binding globulin (TBG) - Clinical Significance:
Triiodothyronine is one of the thyroid hormones present in serum that regulates metabolism. Determination of this hormone concentration is important for the diagnostic differentiation of euthyroid, hyperthyroid and hypothyroid states. The major fraction of total triiodothyronine is bound to the transport proteins (TBG, prealbumin, albumin). Free triiodothyronine (fT3) is the physiologically active form of the thyroid hormone triiodothyronine (T3).
The determination of free T3 has the advantage of being independent of changes in the concentrations of binding properties of the binding proteins; additional determination of a binding parameter (T-uptake, TBG) is therefore unnecessary.
The sequential testing procedure and the use of a labeled antibody reduces the possibility of interference due to altered binding properties of the serum, as can occur with assays employing labeled antigen (analog method).
Also see:
- Reference Range:
2.0-4.0 pg/mL - Day Run:
Sun-Sat (daily) - Time Run:
As received - Time Reported:
4 hours - Test Type:
HORMONE
