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Test Code 28228 T4 Free (Thyroxine)

Important Note

Test subject to Medicare National Coverage Determination (NCD) Thyroid Testing 190.22

The results of this assay can be falsely lowered due to the consumption of Biotin. Please instruct patients to discontinue the use of vitamins or supplements that contain Biotin 12 hours before blood collection.

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Purpose

Thyroid function test. Decreased in hypothyroidism and in the third stage of (painful) subacute thyroiditis; increased with hyperthyroidism, with subacute thyroiditis in its first stage and with thyrotoxicosis due to Hashimoto disease.

 

Performing Laboratory

Copley Hospital

 

Methodology

Bichromatic Rate (LOCI Module)

 

Specimen Requirements

Specimen Type: Blood (Serum)

Preferred: Gold Top

Acceptable: Red Top

Specimen Volume: Full Tube

Specimen Minimum Volume: 2 mL

 

Collection Instructions:

1. Label specimen with patient’s full name, date of birth,

    date & time of collection and person collecting.

2. If delay in specimen transport > 1 hour, centrifuge tube.

3. Refrigerate specimen during transport.

 

Reference Values

Normal: 0.76 - 1.46 ng / dL

 

Stability

Refrigerated: 7 Days

 

Day(s) Performed

Daily

Available STAT

Analytical Time: 1 Day

 

Aliases

T4 Free (Thyroxine)

Thyroxine

Free T4

T4

 

Test Classification & CPT Coding

84439