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Test Code FT4B T4, Free  

Important Note

This test may be affected by biotin interference. Patients on high dose biotin (5mg/day or more) should not have samples drawn until at least 24 hours after the last biotin administration.

Specimen Type

Serum

Container/Tube

Red Top

Offsite Collection Instructions

1. Collect sample following standard collection methods
2. Within 2 hours of collection the sample must be spun and
aliquoted
3. Transport refrigerated (2 – 8˚C)

Turnaround Time

4 hours

Test Includes

N/A

Preferred Volume

0.5 mL

UCMC Collection Instructions

1. Collect sample following standard collection methods
2. Within 2 hours of collection the sample must be received in
Laboratory Service Center
3. Transport room temperature (15 – 25˚C)

STAT Turnaround Time

N/A

Test Usage

Useful when thyroid function disorders are suspected. The
determination of FT4 is also suitable for monitoring
thyrosuppressive therapy.

Critical Results

N/A

Test Limitations

In pregnancy, plasma FT4 measurement by immunoassay is of
limited useor unreliable (2011 Guidelines of the American Thyroid
Association for the diagnosisand management of thyroid disease
during pregnancy and postpartum. (Thyroid 2011; 21:1081-1125).

Furosemide caused elevated FT4 findings at the daily therapeutic
dosage level.

The test cannot be used in patients receiving treatment with
lipid-lowering agents containing D-T4. If the thyroid function is
to be checked in such patients, the therapy should first be
discontinued for 4-6 weeks to allow the physiological state to
become re-established.

Autoantibodies to thyroid hormones can interfere with the
assay.

Binding protein anomalies seen with FDH (familial dysalbuminemic
hyperthyroxinemia), for example, may cause values which, while
characteristic of the condition, deviate from the expected
results.

Fee Code

30184439

Stability: Room Temp

n/a

Stability: Refrigerated

7 days

Stability: Frozen

1 month

Specimen Minimum Volume

0.2 mL

DAY(S) AND TIME(S) PERFORMED

24 hours, 7 days a week including holidays.

STAT DAY(S) AND TIME(S) PERFORMED

N/A

CPT

84439

Method Name

Electrochemiluminescence immunoassay (ECLIA)

Reference Values

0.9 – 1.7 ng/dL

Reject Due To

Whole blood/unspun samples greater than 6 hours will be
rejected.

Synonyms

N/A

Additional Information

N/A

Included in Additional codes

N/A

Coverage Information

N/A