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Test Code T4 T4, Total

Additional Codes

Epic: LAB126

Specimen Required

Collection Container/Tube: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 3.0 mL
Collection Instructions: Centrifuge and separate cells after clot formation and within 4 hours of collection.  Remove serum if testing will be delayed more than 24 hours.

Specimen Minimum Volume

0.3 mL

Specimen Stability

Room temperature: Unacceptable
Refrigerated (on gel): 24 hours
Refrigerated (off gel): 6 days
Frozen: >6 days

Clinical Significance

Thyroxine (T4) is an iodine-containing hormone and is secreted by the thyroid gland.  T4 and its associate thyroid hormone T3 are responsible for regulating diverse biochemical processes throughout the body.  T4 is 99.9% bound to serum thyroxine binding globulin.  Less than 0.05% of the total circulating T4 is unbound and therefore biologically active. Elevated T4 values are seen in patient with overt hyperthyroidism, while T4 levels are generally depressed in patient with hypothyroidism.

Reference Range

4.87 - 11.72 µg/dL

Rejection Due To

Samples stored on gel >24 hours, unlabeled, mislabeled, wrong tube type, hemolyzed, QNS, exceeds specimen stability requirements.

Day(s) and Time(s) Performed

Daily

Report Available

Same day

Method Name

Chemiluminescent microparticle immunoassay (CMIA)

LOINC

3026-2

Limitations

The ARCHITECT Total T4 assay is designed to have a mean potential interference from hemoglobin, bilirubin, triglycerides, and protein of <10% at : 
Hemoglobin ≤ 500 mg/dL
Bilirubin ≤20 mg/dL
Triglycerides ≤ 3000 mg/dL
Protein ≥ 4.5 and ≤ 12 g/dL