Epic Test Code LAB875 Sirolimus, Whole Blood
Additional Codes
MML Code: SIIRO
LIS Code: SRLM
NY State Approved
YesPerforming Laboratory
Mayo Clinic Laboratories in RochesterReporting Name
Sirolimus, BMethod Name
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Whole Blood EDTA | Refrigerated (preferred) | 28 days | |
Ambient | 28 days | ||
Frozen | 28 days |
Specimen Required
Container/Tube: Lavender top (EDTA)
Specimen Volume: 3 mL
Collection Instructions:
1. Draw blood immediately before a scheduled dose.
2. Do not centrifuge.
3. Send whole blood specimen in original tube. Do not aliquot.
Additional Information: Therapeutic range applies to trough specimen collected immediately prior to a.m. dose.
Specimen Type
Whole Blood EDTASpecimen Minimum Volume
1 mL
Reference Values
4-20 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.
Report Available
Same day/1 to 3 daysDay(s) Performed
Monday through Sunday
CPT Code Information
80195
Reject Due To
Gross hemolysis | OK |
Gross lipemia | OK |
Gross icterus | OK |
Clotted specimens | Reject |
Useful For
Monitoring whole blood sirolimus 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
Clinical Information
Sirolimus is a macrolide antibiotic, isolated from Streptomyces hygroscopicus, with potent effects, including suppression of T- and B-cell proliferation and antineoplastic and antifungal activity. It inhibits the protein kinase mTOR (mechanistic target of rapamycin) to arrest the cell cycle; it has no effects on calcineurin and, therefore, can either be used in addition to cyclosporine or tacrolimus or as a substitute in patients intolerant to these drugs.
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Sirolimus is metabolized by cytochrome P450 (CYP) 3A4; thus, blood concentrations are affected by drugs that inhibit or induce this enzyme. The pharmacokinetic interaction between sirolimus and cyclosporine or tacrolimus increases both therapeutic immunosuppression and the toxicity of these agents; lower doses are required with combined use. Adverse effects of sirolimus are generally concentration dependent, making therapeutic drug monitoring essential.
The frequency of monitoring trough concentrations varies on the indication. For example, for kidney transplant recipients, sirolimus is commonly measured at least 3 to 4 days after a loading dose or, if the kidney transplant recipient is receiving cyclosporin, between 5 to 7 days after initiation. Target concentrations vary depending on concomitant therapy, time posttransplant, the desired degree of immunosuppression, and adverse effects. When given with cyclosporine or tacrolimus, the therapeutic range for sirolimus is generally between 4 and 12 ng/mL with minimal added benefit for concentrations greater than10 ng/mL. When sirolimus is given without calcineurin inhibitors, higher trough levels are needed, usually 12 to 20 ng/mL but occasionally up to 20 to 30 ng/mL.
Interpretation
Most individuals display optimal response to sirolimus with trough whole blood levels 4 to 20 ng/mL. Preferred therapeutic ranges may vary by transplant type, protocol, and comedications.
Therapeutic ranges are based on specimens collected at trough (ie, immediately before a scheduled dose). Higher results will be obtained when the blood is collected at other times.
The assay is specific for sirolimus; it does not cross-react with cyclosporine, cyclosporine metabolites, tacrolimus, tacrolimus metabolites, or sirolimus 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.
Specimen Retention Time
14 daysForms
If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:
-Renal Diagnostics Test Request (T830)
-Therapeutics Test Request (T831)