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Test Code Billings Clinic: 4035 Thyroid Panel, Plasma or Serum

Performing Laboratory

Billings Clinic Laboratory: Chemistry

Useful For

Estimating the amount of circulating free thyroxine (free thyroxine index) using the total thyroxine and thyroid binding capacity (T-uptake)

Methodology

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Specimen Requirements

Submit only 1 of the following specimens:

Serum or plasma should be physically separated from cells as soon as possible with a maximum limit of two hours from the time of collection.

 

Plasma

  • Draw blood in a green-top (lithium heparin) tube(s).
  • Spin down and send 1.0 mL of heparinized plasma frozen.

 

Serum

  • Draw blood in a plain, red-top tube(s) or a serum gel tube(s).
  • Spin down and send 1.0 mL of serum frozen

Storage/Stability

Specimen Type Temperature Time
Plasma, Serum Refrigerated 2 days
  Frozen (preferred) 1 month
  Ambient 8 hours

Reject Due To

  • Specimens with apparent contamination
  • Specimens stored at room temperature greater than 8 hours
  • Samples frozen and thawed more than once

Reference Values

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Day(s) Test Set Up

Daily

Test Classification and CPT Coding

84436 - T4, total
84479 - T3, uptake


LCD or NCD test. ICD-10 code is required for this test. When appropriate, obtain a properly executed ABN and submit the ABN with test order(s). See “Medical Necessity and Advanced Beneficiary Notice (ABN) Policy and Form” uner Resources for a copy of a form and additional information.

LOINC Code Information

Reporting Name LOINC Code
T4, Total 3026-2
T3, Uptake 3023-9
FTI (calculation) 32215-6

 

Profile/Testing Information

Profile Information:
Free Thyroxine Index (FTI) (calculation)

T4 (Thyroxine), Total Only
T3 (Triiodothyronine), Uptake