T4/FTI
Test Mnemonic
T4FTI
CPT Codes
- 84436 - QTY (1)
- 84479 - QTY (1)
Aliases
- Free Thyroxine Index
- Thyroxine FTI
Includes
- Total T4
- T4-Uptake
- Free Thyroxin Index FTI calculation
Performing Laboratory
Cleveland Clinic Laboratories
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Plasma | Lithium heparin PST (Lt. Green) | Centrifuge and refrigerate. | Submit in original tube or aliquot into CCL aliquot tube |
Alternate Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 1 mL | Serum | SST (Gold) | Centrifuge and refrigerate. |
Minimum Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 0.6 mL |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | 4 days |
| Refrigerated | 8 days |
| Frozen | 12 months |
Days Performed
Sun - Sat
Turnaround Time
8 hours
Methodology
| Name | Description |
|---|---|
| Electro Chemiluminescence Immunoassay (ECLIA) |
Reference Range
| Free Thyroxin Index FTI calculation | |||||
|---|---|---|---|---|---|
| Sex | Age From | Age To | Type | Range | Range Unit |
| Normal | 5.3 - 10.8 | ug/dL | |||
| T4 | |||||
| Sex | Age From | Age To | Type | Range | Range Unit |
| Days | 364 Days | Normal | 5.5 - 14.5 | ug/dL | 6 Years | 17 Years | Normal | 4.4 - 12.2 | ug/dL | 18 Years | 99 Years | Normal | 5.5 - 10.2 | ug/dL | Male | 1 Years | 5 Years | Normal | 4.4 - 11.7 | ug/dL | Female | 1 Years | 5 Years | Normal | 5.6 - 13.1 | ug/dL |
| T4-Uptake | |||||
| Sex | Age From | Age To | Type | Range | Range Unit |
| 0.91 - 1.19 |
Special Info
Patients taking a biotin dose of up to 5 mg/day should refrain from taking biotin for 4 hours prior to sample collection. Patients taking a biotin dose of 5 to 10 mg/day should refrain from taking biotin for 8 hours prior to sample collection. Patients taking a biotin dose > 10 mg/day should consult with their physician or the laboratory prior to having a sample taken. Clinicians should consider biotin interference as a source of error, when clinically suspicious of the laboratory result.
Clinical Info
Evaluation of suspected hypo or hyperthyroidism