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Free T4 Index (T7)
MessageTest performed at York Hospital Laboratory.
Test Code
FT4INDX
Alias/See Also
T7 FT4 Index
CPT Codes
84436, 84479
Includes
Total T4
T3 Uptake
Free T4 Index
T3 Uptake
Free T4 Index
Preferred Specimen
0.4 mL serum collected in a serum separator tube (SST)
Other Acceptable Specimens
0.4 mL serum collected in a no additive (red-top) tube, transferred to a plastic screw-cap vial
0.4 mL plasma collected in a lithium heparin (green-top) gel separator tube
0.4 mL plasma collected in a lithium heparin (green-top) gel separator tube
Transport Temperature
Refrigerated
Specimen Stability
Room temperature: 4 hours
Refrigerated: 5 days
Frozen: 4 weeks
Refrigerated: 5 days
Frozen: 4 weeks
Methodology
Chemiluminescence
Setup Schedule
Daily
Report Available
Next day
Reference Range
| Test | Ages | Reference Range |
|---|---|---|
| Total T4 | <= 4 days | 11.03 - 21.52 ug/dL |
| 1-4 weeks | 8.23 - 17.17 ug/dL | |
| 1-12 months | 5.90 - 16.31 ug/dL | |
| 1-5 years | 7.30 - 14.99 ug/dL | |
| 6-10 years | 6.37 - 13.28 ug/dL | |
| 11-15 years | 5.52 - 11.73 ug/dL | |
| 16-19 years | 4.20 - 11.81 ug/dL | |
| Adult | 5.53 - 11.00 ug/dL | |
| T3 Uptake | All | 23.5 - 40.5 % |
| Free T4 Index | All | 1.65 - 3.89 ug/dL |
