Home
HelpTest Code LAB127 Thyroxine (T4), Free
Clinical System Name
Thyroxine (T4), Free
FREE T4
Synonyms
FT4
Sample Requirements
Specimen: Whole blood
Container(s): Gold SST, Red, Gold Microtainer, Dark Green/Sodium Heparin, Lt. Green/Lithium Heparin Microtainer, Lavender/EDTA
Preferred Vol: 1.0 mL
Minimum Vol: 0.5 mL
Processing Instructions
Reject due to:
Spin: Y
Aliquot: Y
Temp: 2-8 C
Storage location: CPA refrigerator, FrigD rack. Serum should be removed from separator for storage.
Note: Minimum volume of 1.0 mL serum may be shared with TSH, T4, Free T3, and Free T4
Off-site collection: Spin blood. Transfer serum to plastic aliquot container. Refrigerate.
Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| gel separator with serum | Refrigerated | 24 h |
| separated serum | Room temp | 2 h |
| Refrigerated | 6 d | |
| Frozen -20 C | 4 w |
Availability
| STAT | Performed | TAT |
|---|---|---|
| N | M-Sa, day shift | 1-3 d |
Performing Laboratory
Seattle Children's Laboratory
Department
Department: Chemistry
Location: Chem West
Phone Number: (206) 987-2617
CPT Codes
84439
Methodology
Method: Chemiluminescent microparticle immunoassay (CMIA) by Abbott Alinity i
Analytical Volume: 0.200 mL serum
Limitations:
Reference Range
| Age |
ng/dL |
|---|---|
| 0-14 d | 1.05 - 3.21 |
| 15 - <1 mo | 0.68- 2.53 |
| 1 mo - <1yr | 0.68 - 1.70 |
| >1 yr | 0.70 – 1.48 |
FT4 transitioned platforms from Ortho Vitros 3600 to Abbott Alinity i on August 8, 2022.
There is a 35% negative bias with the new method.