| Laboratory: | Clinical Biochemistry (AUTOMATED) | ||||||||||||||
| Test Name: |
THYROXINE, FREE (FREE T4) - (P)
Test Code:
FT4
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| Clinical Information: |
Free T4 is available as a component of the Thyroid Reflex Testing protocol.
Free T4 will be performed when TSH is < 0.40 mU/L or ≥ 4.3 mU/L Test Indications: This test is used in the evaluation of suspected thyroid dysfunction when measured in conjunction with thyroid stimulating hormone. Free T4 is the unbound and biologically active form & represents only 0.03% of total circulating thyroxine. Patient Preparation Instructions: This test is unaffected by multivitamins (45 - 125 µg biotin) or biotin-only supplements. For additional information see: |
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| Collection Devices: |
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| Specimen Required: |
Plasma: 2.0 mL
Stability 7 days refrigerated, 1 month frozen |
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| Referral: |
Serum: 2.0 mL
Samples must be transferred to an aliquot tube and stored frozen if analysis will not be complete within 48 hours (#110-10-05 Serum / Plasma Separation Procedure & Transport)
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| Requisition: | |||||||||||||||
| Reference Values: |
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| Availability: |
Daily
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| See Also: | |||||||||||||||
| More Information: |
Free T4 is automatically performed when TSH < 0.40 mU/L and ≥ 4.3 mU/L except for ENDO or ENDM. Separate plasma and refrigerate.
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