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HelpTest Code FT4 Free T4
Additional Codes
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Cerner |
NextGen |
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T4 Free |
T4 Free |
Alternate Name(s)
Free T4
FT4
Free thyroxine
Methodology
(Vitros) Immunometric immunoassay, Chemiluminescent
Patient Preparation
None
Collection Instructions
Standard phlebotomy practices.
Specimen Requirements
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Container |
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Stability |
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Rejection Criteria |
Gross Hemolysis Turbid Specimens |
Result Reporting and Reference Values
Reported in ng/dL
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Age |
Low |
High |
|
0-3 Days |
2.0 |
5.0 |
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4days-30 days |
0.9 |
2.2 |
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31 days-18Y |
0.8 |
2.0 |
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18 – 150Y |
0.78 |
2.19 |
Reflex Testing
None
Limitations
The following interpretive data is visible to practitioner: Mefanamic acid, Sodium salicylate, o-Acetylsalicyclic acid (Aspirin), Phenytoin of 10 mg/dL, Bilirubin of 20 mg/dL and Diclofenac could create a significant positive bias.
Useful For
The free fraction of the circulating thyroxine (T4) is considered to exert the main influence on metabolic control. Consequently, the FT4 concentration is believed to be the most direct indicator of an individual’s thyroid status. FT4 concentrations are generally depressed in hypothyroidism and raised in hyperthyroidism. Measurement of FT4 thus provides an aid to the differential diagnosis of thyroid disease.