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Test Code FRT4 T4 (Thyroxine), Free, Serum

Reporting Name

T4 (Thyroxine), Free, S

Useful For

Evaluation of suspected thyroid function disorders using free thyroxine measured together with thyroid-stimulating hormone

Testing Algorithm

See Thyroid Function Ordering Algorithm in Special Instructions.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Serum


Specimen Required


Patient Preparation: For 12 hours before this test do not take multivitamins or dietary supplements containing biotin (vitamin B7), which is commonly found in hair, skin, and nail supplements and multivitamins.

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 1 mL


Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time
Serum Refrigerated (preferred) 14 days
  Frozen  30 days
  Ambient  72 hours

Reference Values

Pediatric

0-5 days: 0.9-2.5 ng/dL

6 days-2 months: 0.9-2.2 ng/dL

3-11 months: 0.9-2.0 ng/dL

1-5 years: 1.0-1.8 ng/dL

6-10 years: 1.0-1.7 ng/dL

11-19 years: 1.0-1.6 ng/dL

 

Adult (≥20 years): 0.9-1.7 ng/dL

 

For SI unit Reference Values, see https://www.mayocliniclabs.com/order-tests/si-unit-conversion.html

Day(s) and Time(s) Performed

Monday through Sunday; Continuously

Test Classification

This test has been cleared or approved by the U.S. Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information

84439

LOINC Code Information

Test ID Test Order Name Order LOINC Value
FRT4 T4 (Thyroxine), Free, S 3024-7

 

Result ID Test Result Name Result LOINC Value
FRT4 T4 (Thyroxine), Free, S 3024-7

Analytic Time

Same day/1 day

Specimen Retention Time

7 days

Reject Due To

Hemolysis

Mild OK; Gross OK

Lipemia

Mild OK; Gross OK

Icterus

Mild OK; Gross OK

Other

NA

 

Method Name

Electrochemiluminescence Immunoassay