Ordering Recommendation

Not recommended for routine thyroid screening.

Mnemonic
T7
Methodology

Quantitative Electrochemiluminescent Immunoassay

Performed

Sun-Sat

Reported

Within 24 hours

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

Serum separator tube or plasma separator tube. Also acceptable: Lavender (EDTA), pink (K2EDTA), or green (sodium or lithium heparin).

Specimen Preparation

Allow specimen to clot completely at room temperature. Separate serum or plasma from cells ASAP or within 2 hours of collection. Transfer 1 mL serum or plasma to an ARUP Standard Transport Tube. (Min: 0.5 mL)

Storage/Transport Temperature

Refrigerated.

Unacceptable Conditions

Grossly hemolyzed specimens.

Remarks
Stability

After separation of cells: Ambient: 4 days; Refrigerated: 8 days; Frozen: 1 year

Reference Interval
Test Number
Components
Reference Interval
  Free Thyroxine Index Calculation FTI 1.7-4.2
0070135 T3 Uptake 28-41% uptake
0070140 Thyroxine
Cord blood 6.60-17.50 µg/dL
0-3 days 5.37-22.40 µg/dL
4-30 days 5.24-23.20 µg/dL
1-23 months 5.37-16.00 µg/dL
2-6 years 5.26-14.80 µg/dL
7-11 years 5.70-14.10 µg/dL
12-19 years 4.74-14.60 µg/dL
20 years and older 5.10-14.10 µg/dL

Interpretive Data

Thyroxine, Free (FT4) (0070138) is the preferred test alternative for T3 uptake and Free Thyroxine Index tests.

Compliance Category

FDA

Note

FTI  = Free Thyroxine Index

Hotline History
N/A
CPT Codes

84479; 84436

Components
Component Test Code* Component Chart Name LOINC
0070135 T3 Uptake 3050-2
0070140 Thyroxine 3026-2
0070196 Free Thyroxine Index Calculation 32215-6
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Free Thyroxine Index
  • FT4 Index
  • FTI
  • T3 uptake
  • T7
  • thyroxine
  • Thyroxine Index
Thyroid Panel