Test Directory

FTI (Free Thyroxine Index)

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Updated Test Information:

Test Description
FTI (Free Thyroxine Index)
Synonym(s)
FTI
Test ID
FTI
General Information
Includes T4, T4 Uptake, and calculation of FTI
Specimen Type
Serum
Alternate Specimen Type
Red, Li‑heparin, K2‑EDTA and K3‑EDTA plasma
Specimen Requirements
SST
Stability
4 days at 20‑25 °C,
8 days at 2‑8 °C,
12 months at ‑20 °C (± 5 °C) Freeze only once
Methodology
electrochemiluminescence immunoassay “ECLIA”
Estimated TAT
0-2 days
Testing Schedule
Monday-Saturday
CPT Code(s)
84479
84436
Minimum Sample Volume
1 mL
Pediatric Min. Volume (if applicable)
500 uL
Reference Range
0-5 days 5.1-20.8 mcg/dL
6 days-2 months 5.5-18.0 mcg/dL
3-11 months 5.7-16.8 mcg/dL
1-5 years 5.9-15.0 mcg/dL
6-10 years 6.0-13.9 mcg/dL
11-19 years 5.9-13.2 mcg/dL
≥20 years 4.8-12.7 mcg/dL
Performing Lab
Incyte Diagnostics
LOINC Code(s)
32215-6