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, Free
MessageTest performed at York Hospital Laboratory.
Test Code
FT4
Alias/See Also
Free T4
CPT Codes
84439
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
Transport Temperature
Refrigerated
Specimen Stability
Room temperature: 4 hours
Refrigerated: 7 days
Frozen: 4 weeks
Refrigerated: 7 days
Frozen: 4 weeks
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Plasma samples
Methodology
Chemiluminescence
Setup Schedule
Daily
Report Available
Next Day
Reference Range
Age | Free T4 (ng/dL) |
---|---|
<=4 Days | 2.18 - 5.28 |
1-4 Weeks | 0.93 - 2.33 |
1-12 Months | 0.78 - 1.79 |
1-5 Years | 0.78 - 2.10 |
6-10 Years | 0.81 - 2.10 |
11-19 Years | 0.78 - 2.02 |
Adult | 0.78 - 2.19 |
Clinical Significance
The FT4 concentration is believed to be the most direct indicator of an individual's thyroid status. FT4 concentrations are generally depressed in hypothyroidism and raised in hyperthyroidism. Measurement of FT4 thus provides an aid to the differential diagnosis of thyroid disease. FT4 concentrations are independent of the concentration of thyroid hormone binding proteins and may therefore be measured in patients with elevated or reduced binding protein concentrations without the need for additional tests of binding capacity.