Triiodothyronine (T3), Free by Equilibrium Dialysis/LC-MS/MS
Also known as: T3 FREE SP
Use
The Triiodothyronine (T3), Free by Equilibrium Dialysis/LC-MS/MS test is used to measure the levels of free triiodothyronine in the blood, which is a critical parameter in evaluating thyroid function. T3 is one of the two primary hormones produced by the thyroid gland, and its free form is the biologically active form, making its measurement crucial for diagnosing and managing thyroid disorders. This test aids in the differential diagnosis of hyperthyroidism and monitoring thyroid status, especially in individuals with altered thyroid-binding protein levels or conditions affecting hormone distribution such as pregnancy.
Special Instructions
The test requires the collection of serum or plasma, ensuring prompt separation from cells within 45 minutes to prevent degradation. It is essential to follow precise specimen handling and transportation guidelines to maintain the integrity and stability of the sample. The test is not performed at ARUP Laboratories, therefore separate specimens should be submitted when ordering multiple tests. New York state approval confirms its compliance with regional regulatory standards, ensuring reliable clinical application.
Limitations
This test is performed using a non-FDA approved method developed by a commercial laboratory and is not validated for clinical use by the FDA. It may not be suitable for diagnosing certain thyroid disorders due to potential variability introduced by different laboratory methods. Interference with the equilibrium dialysis step or mass spectrometry measurement could result in inaccurate free T3 levels. Factors such as sample contamination, improper handling, or suboptimal pre-analytical conditions could also affect test outcomes. Therefore, clinical correlation with other thyroid function tests and patient presentation is necessary.
New York Approved
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 29239-1
Result Turnaround Time
8-14 days
Related Documents
For more information, please review the documents below
Specimen
Plasma
Volume
1 mL
Minimum Volume
0.3 mL
Container
ARUP standard transport tube
Collection Instructions
Separate from cells ASAP or within 45 minutes of collection. Use plain red or lavender (K2EDTA), SST, lavender (K3EDTA), pink (K2EDTA), plasma preparation tube (PPT), or green (sodium heparin) for collection.
Storage Instructions
Frozen; Also acceptable: Refrigerated or room temperature.
Causes for Rejection
Specimen submitted in gel-barrier tube.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 5 days |
| Refrigerated | 5 days |
| Frozen | 10 weeks |