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HelpTest Code FT4 or LAB2388 Free T4, Serum or Plasma
Specimen Requirements
| Container Type: |
Optimal: Gold or Mint* *For STAT requests |
|
Acceptable: Red or Green |
|
| Optimal Collection Volume: |
4.5mL; full tube |
| Minimum Volume: |
1 mL whole blood |
| Collection Instructions: |
Gently invert the sample 5-6 times after collection. |
| Specimen Transport: |
Refrigerate |
| Processing Instructions: |
1. If serum, allow the specimen to clot for 30 minutes. 2. Centrifuge specimen within 2 hours of collection. 3. After centrifugation, specimen tubes without a gel barrier should have the serum or plasma aliquoted to a false bottom container. 4. Keep serum or plasma refrigerated until testing can be performed. |
Specimen Stability
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum* | Refrigerated | 7 days |
| Frozen | 30 days |
*Note: Heparinized plasma in gel separator tubes is less stable than serum and is only suitable for add-on testing up to 2 days following sample collection.
Specimen Rejection Criteria
| Hemolysis | Mild OK; Moderate OK; Gross Reject |
| Lipemia | Mild OK; Moderate OK; Gross Reject |
| Icterus | Mild OK; Moderate OK; Gross Reject |
| Other | Quantity not sufficient |
Useful For
Free T4 is measured together with TSH when thyroid function disorders are suspected. The determination of FT4 is also suitable for monitoring thyrosuppressive therapy.
Methodology
Roche Cobas - Electrochemiluminescence assay
Reference Ranges
0.8-1.7 ng/dL
Day(s) Performed
24/7
Expected TAT
Same day
Performing Laboratory
Bronson Laboratory, Chemistry - Kalamazoo, Battle Creek, Paw Paw, South Haven
Sample Retention Time
7 days
CPT Code
84439
LOINC Code
3024-7