Tacrolimus, Blood
Use
Monitoring whole blood tacrolimus concentration is crucial during therapy, particularly when coadministered with cytochrome P450 (CYP) 3A4 substrates, inhibitors, or inducers. It aids in adjusting doses to optimize immunosuppression while minimizing toxicity and evaluating patient compliance. Tacrolimus, a macrolide antibiotic derived from the fungus Streptomyces tsukubaensis, inhibits calcineurin to suppress T cells and is metabolized by cytochrome P450 (CYP) 3A4. The narrow therapeutic range requires careful monitoring to prevent adverse effects, especially at high concentrations.
Special Instructions
Preferred therapeutic range applies to trough specimens collected immediately before a dose. Collect blood immediately before a scheduled dose; do not centrifuge or aliquot after collection. The test has not been cleared or approved by the US Food and Drug Administration but is consistent with CLIA requirements.
Limitations
The assay is specific to tacrolimus and does not cross-react with cyclosporine or sirolimus and their metabolites. Results may differ by approximately 30% compared to immunoassay methods, due to the liquid chromatography tandem mass spectrometry methodology used. Blood drawn at times other than immediately before a scheduled dose may yield higher than expected results due to post-dose elevation.
New York Approved
Methodology
Mass Spectrometry (LC-MS/MS)
Biomarkers
LOINC Codes
- 77348-1
- 77348-1
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
3 mL
Minimum Volume
1 mL
Container
Lavender top (EDTA)
Collection Instructions
Draw blood immediately before a schedule dose. Do not centrifuge. Send whole blood specimen in original tube. Do not aliquot.
Causes for Rejection
Clotted specimens
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |