| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # |
T4 (Thyroxine)
MessageTest performed at York Hospital Laboratory.
Test Code
T4
Alias/See Also
Thyroxine
CPT Codes
84436
Preferred Specimen
0.2 mL serum collected in a serum separator tube (SST)
Other Acceptable Specimens
0.2 mL serum collected in a no additive (red-top) tube, transferred to a plastic screw-cap vial 0.2 mL plasma collected in a lithium heparin (green-top) gel separator tube
Instructions
Separate serum or plasma from the cells within 4 hours of collection.
Transport Temperature
Refrigerated
Specimen Stability
Room temperature: 4 hours Refrigerated: 5 days Frozen: 4 weeks
Methodology
Chemiluminescence
Setup Schedule
Daily
Report Available
Next Day
Reference Range
| Age | Total T4 (ug/dL) |
|---|---|
| <=4 Days | 11.03 - 21.52 |
| 1-4 Weeks | 8.23 - 17.17 |
| 1-12 Months | 5.90 - 16.31 |
| 1-5 Years | 7.30 - 14.99 |
| 6-10 Years | 6.37 - 13.28 |
| 11-15 Years | 5.52 - 11.73 |
| 16-20 Years | 4.20 - 11.81 |
| Adult | 5.53 - 11.00 |
Clinical Significance
In most patients the total T4 level is a good indicator of thyroid status, however it can sometimes be inadequate, and diagnostic efficiency may be improved by use of a total T4 test in conjunction with other tests. T4 levels may be altered in conditions affecting the capacity of the thyroid hormone binding proteins, e.g. pregnancy, when a test for triiodothyronine (T3) or T4 uptake may be used with the total T4 result to calculate the free T4 indix (FT4I) to estimate the level of metabolically active free T4.
