Test Directory

Free T4

Loinc

Expected Turnaround

24 hours

Information

Free T4 is a useful tool in clinical routine diagnostics for the assessment of the thyroid status. It should be measured together with TSH if thyroid disorders are suspected and is also suitable for monitoring thyrosuppressive therapy

Collection Information

Samples should not be taken from patients receiving therapy with high biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin administration.

Methodology

Electrochemiluminescence-immunoassay (ECLIA)

Limitations

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

Rejection Criteria

Specimen Stability

Refrigerated: 7 days Frozen: 1 month

Alias

Free T4; T4, free

Container Type

Serum, gel separator, SST

Minimum Volume

1 ML

Age Range

0 - 999

Sex

Generic

Units of Measure

ng/dL

Reference Range

0.93 ng/dL - 1.7 ng/dL

Panic Range