Thyroxine (T4) Free, Direct
Test Code: 001974
Performing Lab: LabCorp
CPT Code: 84439 001
Synonym
Free T4, Direct; Free Thyroxine; T4, Free, Direct T4, Free, Direct; Unbound T4
Specimen Type
Serum (preferred) or plasma
Specimen Container
Red-top tube, gel-barrier tube, OR green-top (lithium heparin) tube. Do NOT use oxalate, EDTA, or citrate plasma.
Volume
1 mL
Minimum Volume
0.7 mL (NOTE: This volume does NOT allow for repeat testing.)
Specimen Handling
If a red-top tube or plasma tube is used, transfer separated serum or plasma to a plastic transport tube.
Patient Prep
Heparin has been reported to have in vivo and in vitro effects on free T4 assay. Hence samples should not be collected during or soon after the administration of this anticoagulant.
Unacceptable Conditions
Citrate plasma specimen; improper labeling
Temperature
Room temperature
Methodology
Electrochemiluminescence Immunoassay (ECLIA). This assay is performed on the Roche cobas instrument in multiple laboratories throughout Labcorp.
Stability
Room Temperature: 14 days
Refrigerated: 14 days
Frozen: 14 days
Refrigerated: 14 days
Frozen: 14 days
| Result Code | Result Name | LOINC |
|---|---|---|
| 019745 | T4,Free(Direct) | 3024-7 |
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