T3 Free

Test ID: 

704291

CPT code:

84481

Synonyms:

Free T3
(T3), Free
Triiodothyronine (T3), Free

Clinical Use:

Evaluate thyroid function and assess abnormal binding protein disorders

Test Information:

Triiodothyronine (T3) normally represents only approximately 5% of the thyroid hormone and like thyroxine is almost entirely bound to the carrier proteins, with only 0.25% of the total being in the free state. Measurement of free triiodothyronine is of value in confirming the diagnosis of hyperthyroidism, when an elevated free or total thyroxine level is found. Abnormal total and free triiodothyronine concentrations may appear in T3 toxicosis, in the presence of normal thyroxine levels. Free T3 levels are unaffected by carrier protein variation.

Specimen Type:

Serum

Requested Volume: 

0.8 mL

Minimum Volume: 

0.3 mL (Note: This volume does not allow for repeat testing.)

Container Type: 

Red-top tube or gel-barrier tube

Collection:

If a red-top tube is used, transfer separated serum to a plastic transport tube.

Storage Instructions:

Room temperature

Stability Requirements:

Rejection Criteria

Citrate plasma specimen; improper labeling