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HelpTest Code T3-FREE Triiodothyronine, Free
Synonyms/Keywords
T-3, Free, T-3 Free, Free T3, FT3
Specimen Requirements
| Fasting Required | Specimen Type | Preferred Container/Tube | Acceptable Container/Tube | Specimen Volume | Specimen Minimum Volume (allows for 1 repeat) |
Pediatric Minimum Volume (no repeat) |
|---|---|---|---|---|---|---|
| No | Plasma/Serum | Lithium Heparin Plasma Separator Tube (PST) |
Lithium Heparin Green Top Tube (GTT), Serum Separator Tube (SST), Red Top Tube (RTT) |
1 mL | 0.5 mL | 0.3 mL |
- GTT/RTT- physically separate plasma or serum from contact with cells as soon as possible of before transport.
- Separate from cells within 30 minutes to minimize uptake of corticosteroids by RBCs
Collection/Processing Instructions
Samples collected in a RTT must be removed from the cells within one hour for storage or transport. Samples collected in gel barrier tubes must be removed from the primary tube prior to transporting to Marshfield.
DO NOT send the primary collection tube.
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
|
Plasma/Serum |
Ambient | 8 hours |
| Refrigerated | 2 days | |
| Frozen | >2 days |
- Thaw samples no more than 3 times
Rejection Criteria
Gross Hemolysis Gross Icterus
Test Information
See Clinical Practice Guidelines: Thyroid Function Ordering Algorithm for more information
Interferences
Human Anti-Murine Antibodies (HAMA) may develop leading to test interference in patients receiving murine-based agents for chemotherapy or tumor-imaging studies.
Reference Range Information
| Performing Location | Reference Range |
|---|---|
| Marshfield | 0 to <1 year: 2.8 4.5 pg/mL 1 to <15 years: 2.6 4.0 pg/mL Female 15 to <19 years: 2.3 3.5 pg/mL Male 15 to <19 years: 2.5 3.7 pg/mL Adult (>19 years): 2.5 3.9 pg/mL |
Marshfield Labs Performing Department
Marshfield Labs Chemistry
Performing Information
| Performing Location | Day(s) Test Performed | Analytical Time | Methodology/Instrumentation |
|---|---|---|---|
| Marshfield | Monday through Sunday | Less than 2 hours | Beckman Coulter DXI |
CPT Codes
| CPT | Modifier (if needed) |
Quantity | Description | Comments |
|---|---|---|---|---|
| 84481 | 1 |
Outreach CPT Codes
| CPT | Modifier (if needed) |
Quantity | Description | Comments |
|---|---|---|---|---|
| 84481 | 1 |
Ordering Applications
| Ordering Application | Description |
|---|---|
| Cerner | Triiodothyronine, Free |