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. Also acceptable: Lavender (K2EDTA or K3EDTA), pink (K2EDTA), or green (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 Effective February 22, 2022.
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 4.50-11.70 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