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HelpTest Code LAB126 Thyroxine Level
Clinical System Name
T4
Synonyms
Total T4
TT4
T4
Sample Requirements
Specimen: Whole blood
Container(s): Gold SST, Red, Gold Microtainer, Lavender/EDTA, Lt. Green/Lithium Heparin, Dark Green/Sodium Heparin
Preferred Vol: 1.0 mL
Minimum Vol: 0.5 mL
Processing Instructions
Reject due to: gross lipemia
Spin: Y
Aliquot: Y
Temp: 2-8 C
Storage location: CPA refrigerator, FrigD rack. Serum/plasma should be removed from separator for storage.
Note: Minimum volume of 0.5 mL serum may be shared with TSH, T4, free T3, and free T4
Off-site collection: Spin blood. Transfer serum/plasma to plastic aliquot container. Note whether patient is on endocrine therapy. Refrigerate.
Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| gel separator with serum/plasma | Refrigerated | 48 h |
| separated serum/plasma | Room temp | 2 h |
| Refrigerated | 5 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
84436
Methodology
Method: Chemiluminescent microparticle immunoassay (CMIA) by Abbott Alinity i
Analytical Volume: 0.200 mL serum/plasma
Limitations: Turbidity may affect results.
Reference Range
| Age |
(mcg/dL) |
|---|---|
| < 1 mo | 4.2 - 14.9 |
| 1 mo - <1 yr | 5.9 - 13.7 |
| 1 - <9yr | 6.2 - 10.3 |
| 9 - <12yr | 5.5 -9.3 |
| 12 - <14 yr | 5.1 - 8.3 |
| 14 - <19 yr | 5.5 - 13.0 |
| > 19 yr | 4.9 - 11.7 |
Total T4 transitioned platforms from Ortho Vitros 3600 to Abbott Alinity i on August 8, 2022.
There is a 20% negative bias with the new method.