Thyroxine, Free by Equilibrium Dialysis/HPLC-Tandem Mass Spectrometry
Also known as: FT4 ED-TMS
Use
This test is useful to evaluate free thyroxine (FT4) status in individuals with protein-binding abnormalities. It is specifically recommended for assessing thyroid function in the presence of such conditions. It is particularly relevant when medications may induce transient changes in FT4 concentrations. However, it is not recommended for patients currently on heparin treatment due to potential false elevation of FT4 concentrations.
Special Instructions
This test is New York state approved. It is recommended to separate serum from cells or gel as soon as possible or within two hours of collection. A plain red or serum separator tube (SST) should be used for collection. Transfer at least 2 mL of serum to an ARUP Standard Transport Tube.
Limitations
It is important to note that this test is not recommended for the routine evaluation of thyroid disorders. The preferred test for such evaluations is Thyroxine, Free (Free T4) (0070138). Errors in FT4 concentration can occur due to medications and conditions like heparin treatment, which may lead to falsely elevated results. Additionally, plasma specimens are unacceptable for this test.
New York Approved
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 6892-4
Result Turnaround Time
2-6 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2 mL
Minimum Volume
0.3 mL
Container
ARUP Standard Transport Tube
Collection Instructions
Separate from cells or gel ASAP or within 2 hours of collection. Transfer 2 mL serum to an ARUP Standard Transport Tube. (Min: 0.3 mL)
Storage Instructions
Refrigerated.
Causes for Rejection
Plasma specimens.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 4 days |
| Refrigerated | 2 weeks |
| Frozen | 1 month |