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HelpTest Code FT3 Free T3
Additional Codes
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Cerner |
NextGen |
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Free T3 |
Free T3 |
Alternate Name(s)
FT3
Free Triiodothyronine
Methodology
Competitive Immunoassay
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 |
Result Reporting and Reference Values
Reported in pg/mL
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Age |
Gender |
Low |
High |
Critical Low |
Critical High |
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0-14 Days |
All |
3.04 |
12.4 |
N/A |
N/A |
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14 Days-4Y |
All |
3.49 |
7.42 |
N/A |
N/A |
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4Y-13Y |
All |
4.34 |
6.97 |
N/A |
N/A |
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13Y-18Y |
Male |
4.13 |
6.72 |
N/A |
N/A |
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13Y-18Y |
Female |
3.7 |
6.07 |
N/A |
N/A |
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19Y -150Y |
All |
2.77 |
5.27 |
N/A |
N/A |
Reflex Testing
None
Limitations
- The results from this or any other diagnostic test should be used and interpreted only in the context of the overall clinical picture.
- Thyroid hormone autoantibodies in serum samples may cause interference in free-hormone immunoassays. Results which are inconsistent with clinical observations indicate the need for additional testing.
- Heat treated samples give elevated FT3 values due to protein denaturation and disturbance of the FT3/T3 equilibrium. In highly processed sera, the thyroid hormone binding capacity may be reduced, leading to elevated FT3 results.
- Certain drugs and clinical conditions are known to alter Free T3 concentrations in vivo. When interpreting FT3 results, note the potential effects of certain drugs on the free-hormone equilibrium.
Useful For
The free fraction of the circulating triiodothyronine (T3) is considered to exert the main influence on metabolic control. In hyperthyroidism, FT3 concentrations are generally elevated and give efficient discrimination at the euthyroid/toxic borderline, providing an effective method for confirming hyperthyroidism and monitoring of its treatment. In hypothyroidism, FT3 concentrations tend to be lower, but the decrease is insufficient to give clear diagnostic information. FT3 concentrations are independent of the concentration of thyroid hormone-binding proteins, and may be measured in patients with elevated or reduced binding protein concentrations without the need for additional tests of binding capacity.