Home
HelpTest Code FRT4D T4 (Thyroxine), Free, Dialysis, Serum
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumAdvisory Information
The routine free thyroxine test (FRT4 / T4 [Thyroxine], Free, Serum) is faster and provides useful information in most patients.
Necessary Information
Include name and telephone number of contact physician.
Specimen Required
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 2.6 mL
Collection Instructions:
1. Draw blood immediately before next scheduled dose.
2. Centrifuge and aliquot serum into plastic vial within 2 hours of draw.
Specimen Minimum Volume
1.2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 28 days | |
| Frozen | 21 days | ||
| Ambient | 7 days |
Reference Values
0.8-2.0 ng/dL
Reference values apply to all ages.
Day(s) and Time(s) Performed
Monday, Wednesday, Thursday; 3 p.m.
CPT Code Information
84439
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Method Name
Equilibrium Dialysis/Tandem Mass Spectrometry (MS/MS)