Test Directory

Direct measurement of FT3 by equilibrium dialysis, high-pressure liquid chromatography, and tandem mass spectrometry (ED-HPLC/MS-MS) provides enhanced accuracy over commonly used analog (automated) methods and is not affected by clinical conditions that impact protein binding capacity.

Examples of clinical conditions in which the FT3 by dialysis and MS/MS method may be preferred include congenital absence of thyroxine-binding protein (TBG); pregnancy; administration of oral contraceptives or hormone therapy; administration of atypical antipsychotic medications; malignancy or other critical illnesses.

Preferred Specimen Type: Serum

Alternate Specimen Type: Plasma

Preferred Collection Container: Red Top, Plain

Alternate Collection Container: Gold Top, Serum Separator, Lavender Top (EDTA), or Green Top (Sodium Heparin)

Desired Specimen Volume: 1 mL

1. Collect a red top, plain tube via venipuncture.

1. Separate serum from cells within 45 minutes of collection.
2. Transfer 1 mL of serum to a LabCorp PP transpak frozen purple tube.

Transport to the laboratory frozen. 

• Whole blood

See patient report.

• Free T3
• Free Triiodothyronine (T3)
• FT3
• Triiodothyronine (T3), Free, Dialysis and LC/MS-MS (Endocrine Sciences)