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Test Code FT3 Free T3

Specimen and Container/Tube

Specimen Type: Plasma

Preferred Specimen: Li-Heparin Mint Green Top

Other Acceptable specimens: Serum/Gold Top, Serum/Red Top, Plasma/Lavendar K2 Top, Plasma/Lavendar K3 Top

Specimen Handling and Transport Instructions

UCMC Onsite Instructions: 

  • Collect specimen per standard collection procedure and send to laboratory immediately. 

 

UCMC Offsite and UC MedLab Outreach Instructions: 

  • Samples should be centrifuged within 2 hours of collection.
  • Centrifuge specimens at >2500 x g for 10 minutes at room temperature.
  • Aliquot sample into plastic transport tube containing a minimum of 0.2 mL of specimen.
  • Samples must be room temperature at 20-25oC.

Rejection Criteria

  • Common specimen rejected situations include: incorrect specimen type, insufficient volume, missing or incomplete specimen identifiers, incorrect specimen transport, or specimens outside stability limits. 
  • Specimens that are clotted or grossly hemolyzed.
  • Specimens that were transported unspun/whole blood and draw time is greater than 6 hours

Reference Values

Test

Age

Sex

Reference Range

FT3

All

All

230 - 420 pg/dL

Critical Values

Analyte

Unit

Low

High

Age

N/A

N/A

N/A

N/A

N/A

CPT Codes

84481

LOINC Codes

14928-6

Volume

Preferred Volume: 0.5 mL

Minimum Volume: 0.2 mL

Specimen Stability

Storage Temperature

Stability

Room Temperature

7 days

Refrigerated

5 days

Frozen

30 days

Collection Instructions

Collect specimen per standard laboratory collection procedures. 

 

Test Components

Free Triidothyronine

Clinical Indications

Free T3 is a useful tool in clinical routine diagostics for the assessment of the thyroid status. Free T3 measurements support the differential diagnosis of thyroid disorders, are needed to distinguish different forms of hyperthyroidism, and to identify patients with T3 thyrotoxicosis.

Methodology

Electrochemiluminescence immunoassay (ECLIA) (Roche Diagnostics)

Additional Information

  • Results should always be assessed in conjunction with patient's medical history, clinical examination and other findings.
  • Any infuence that might affect the binding behavior of the binding proteins can alter the result of the fT3 test, (e.g. drugs, NTIs (Non-Thyroid-Illness) or patients suffering from FDH (Familial Dysalbuminemic Hyperthyroxinemia)).
  • Samples for fT3 determinations cannot be diluted, as T3 in the blood is present in free and protein-bound forms which are in equilibrium. A change in the concentration of the binding proteins alters this equilibrium.
  • In rare cases, interference due to extermely high titers of antibodies to analyte-specific antibodies, streptavidin or ruthenium can occur.

Turnaround Time

Turnaround times are relative to the time the specimen is received in the test laboratory. 

 

STAT Turnaround Time: Not available as STAT test

Routine Turnaround Time: up to 4 hours

Testing Schedule:  24/7

Synonyms/Keyword Search

T3 (Triiodothyronine), Free, Serum, Free T3 (Triiodothyronine), FT3 (Free Triiodothyronine), Triiodothyronine, Free, fT3

Last Review Date

1/26/23