T4 (Thyroxine), Free, Dialysis, Serum
Use
Determining thyroid status of sick, hospitalized patients. Useful for patients in whom abnormal binding proteins have been identified. It is also possibly useful in pediatric patients to determine thyroid function status. Measurement of FT4 by equilibrium dialysis offers more precise results in situations with interfering proteins.
Special Instructions
For ordering: If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen. Include name and telephone number of contact physician. Preferred specimen collection is right before next scheduled dose.
Limitations
Certain drugs like Heparin, various salicylates, and other specified medications may cause short-term fluctuations in free thyroxine levels, potentially impacting the accuracy of measurements. These fluctuations can create diagnostic confusion, along with improper specimen collection and handling. Automated analog immunoassays usually give accurate results, but abnormal types or quantities of binding proteins in patients may interfere.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 6892-4
- 6892-4
Result Turnaround Time
3-8 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
2.6 mL
Minimum Volume
1.2 mL
Container
Preferred: Red top, Acceptable: Serum gel; Submission: Plastic vial
Collection Instructions
Collect specimen immediately before next scheduled dose. Within 2 hours of collection, centrifuge, and aliquot serum into a plastic vial.
Causes for Rejection
Gross hemolysis, gross lipemia, gross icterus
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 28 days |
| Frozen | 21 days |