T4/FTI




Test Mnemonic

T4FTI

CPT Codes

  • 84436 - QTY (1)
  • 84479 - QTY (1)

Aliases

  • Free Thyroxine Index
  • Thyroxine FTI

Performing Laboratory

Cleveland Clinic Laboratories


Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
1 mLPlasmaLithium 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 mLSerumSST (Gold) Centrifuge and refrigerate. 

Minimum Specimen Requirements

Volume Type Container Collect Temperature Transport Temperature Special Instructions
0.6 mL     

Stability

Environmental Condition Description
Ambient4 days
Refrigerated8 days
Frozen12 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
       Normal5.3 - 10.8ug/dL
T4
Sex Age From Age To Type Range Range Unit
   Days364 DaysNormal5.5 - 14.5ug/dL
 6 Years17 YearsNormal4.4 - 12.2ug/dL
 18 Years99 YearsNormal5.5 - 10.2ug/dL
Male1 Years5 YearsNormal4.4 - 11.7ug/dL
Female1 Years5 YearsNormal5.6 - 13.1ug/dL
T4-Uptake
Sex Age From Age To Type Range Range Unit
       Freetext0.91 - 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