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HelpTest Code TAKRO Tacrolimus, Blood
Reporting Name
Tacrolimus, BUseful For
Monitoring whole blood tacrolimus concentration during therapy, particularly in individuals coadministered cytochrome P450 (CYP) 3A4 substrates, inhibitors, or inducers
Adjusting dose to optimize immunosuppression while minimizing toxicity
Evaluating patient compliance
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Whole Blood EDTASpecimen Required
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions:
1. Draw blood immediately before a schedule dose.
2. Do not centrifuge.
3. Send whole blood specimen in original tube. Do not aliquot.
Additional Information: Therapeutic range applies to trough specimens collected immediately prior to a.m. dose.
Specimen Minimum Volume
1 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Whole Blood EDTA | Refrigerated (preferred) | 14 days | |
| Ambient | 14 days | ||
| Frozen | 14 days |
Reference Values
5.0-15.0 ng/mL (Trough)
Target steady-state trough concentrations vary depending on the type of transplant, concomitant immunosuppression, clinical/institutional protocols, and time post-transplant. Results should be interpreted in conjunction with this clinical information and any physical signs/symptoms of rejection/toxicity.
Day(s) Performed
Monday through Sunday
CPT Code Information
80197
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| TAKRO | Tacrolimus, B | 77348-1 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| 35145 | Tacrolimus, B | 77348-1 |
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.Clinical Information
Tacrolimus is a macrolide antibiotic derived from the fungus Streptomyces tsukubaensis. Like cyclosporine, tacrolimus inhibits calcineurin to suppress T cells. Tacrolimus is metabolized by cytochrome P450 (CYP) 3A4; thus, its concentrations are affected by drugs that inhibit (calcium channel blockers, antifungal agents, some antibiotics, grapefruit juice) or induce (anticonvulsants, rifampin) this enzyme. Tacrolimus has a narrow therapeutic range, and adverse effects are common, particularly at high doses and concentrations, making therapeutic drug monitoring essential.
Since 90% of tacrolimus is in the cellular components of blood, especially erythrocytes, whole blood is the preferred specimen for analysis of trough concentrations. Target steady-state concentrations vary depending on clinical protocol, the presence or risk of rejection, time from transplant, type of allograft, concomitant immunosuppression, and side effects (mainly nephrotoxicity). Optimal trough blood concentrations are generally between 5.0 and 15.0 ng/mL. Higher levels are often sought immediately after transplant, but as organ function stabilizes at about 4 weeks from transplant, doses are generally reduced in stable patients for most solid organ transplants. Trough concentrations should be maintained below 20 ng/mL.
Interpretation
Most individuals display optimal response to tacrolimus with trough whole blood levels of 5.0 to 15.0 ng/mL. Preferred therapeutic ranges may vary by transplant type, protocol, and comedications.
Therapeutic ranges are based on specimen collected at trough (ie, immediately before a scheduled dose). Higher results will be obtained when the blood is drawn at other times.
The assay is specific for tacrolimus; it does not cross-react with cyclosporine, cyclosporine metabolites, sirolimus, sirolimus metabolites, or tacrolimus metabolites. Results by liquid chromatography with detection by tandem mass spectrometry are approximately 30% less than by immunoassay.
Cautions
The recommended therapeutic range applies to trough specimens collected immediately before a dose. Blood drawn at other times will yield higher results.
Clinical Reference
1. Kahan BD, Keown P, Levy GA, Johnston A. Therapeutic drug monitoring of immunosuppressant drugs in clinical practice. Clin Ther. 2002;24(3):330-350
2. Scott LJ, McKeage K, Keam SJ, Plosker GL. Tacrolimus: a further update of its use in the management of organ transplantation. Drugs. 2003;63(12):1247-1297
3. Milone MC, Shaw LM: Therapeutic drugs and their management. In: Rifai N, Chiu RWK, Young I, Burnham CAD, eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier; 2023:420-453
Method Description
Blood specimens are subjected to protein precipitation. The resulting supernatant is analyzed by liquid chromatography tandem mass spectrometry.(Bjergum MW, Jannetto PJ, Langman LJ. Simultaneous determination of tacrolimus and cyclosporine A in whole blood by ultrafast LC-MS/MS. Methods Mol Biol. 2019;1872:111-118. doi:10.1007/978-1-4939-8823-5_11)
Report Available
Same day/1 to 3 daysSpecimen Retention Time
14 daysReject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
| Clotted specimens | Reject |
Method Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Forms
If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
-General Request (T239)
-Renal Diagnostics Test Request (T830)
-Therapeutics Test Request (T831)