Sirolimus
Label Mnemonic: SIR
Epic Lab Code: LAB898
Downtime Form: A-1a Therapeutic Drug Assay Requisition
Chemistry
6240 RCP
356-3527
Specimen(s):
Whole Blood
Collection Medium:
Lavender top tube 3 mL (EDTA)
Minimum:
2/3 full in lavender top (EDTA) tube or ONE lavender top (EDTA) microtube for pediatric patients.
Testing Schedule:
Batch analysis performed on Mondays, Wednesdays, and Fridays. Samples need to be in lab 0900 for results at 1200.
Reference Range:
5-30 ng/mL
Comments:
Everolimus (Zortress®, Afinitor®) cross-reacts significantly with the sirolimus immunoassay. Sirolimus blood concentrations cannot be determined reliably in patients whose blood has both sirolimus and everolimus. This can occur when patients are being transitioned from sirolimus to everolimus or everolimus to sirolimus.

Analysis performed using the Abbott Diagnostics Sirolimus immunoassay on the Architect platform. The general therapeutic range for sirolimus is 5-30 ng/mL. The optimal therapeutic range for a given patient may differ from this suggested range based on the indication for therapy, treatment phase (initiation or maintenance), use in combination with other drugs, time of specimen collection relative to prior dose, type of transplanted organ, and/or the therapeutic approach of the transplant center. Sirolimus whole blood concentrations can be measured by either immunoassay or chromatographic methodologies. These two methodologies are not directly interchangeable, and the measured sirolimus whole blood concentration depends on the methodology used. Reference ranges may vary according to the specific immunoassay or HPLC-MS/MS test. Generally, immunoassays have been reported to have a positive bias relative to HPLC-MS/MS assays due to the detection of antibody cross- reactivity with sirolimus metabolites.
Methodology:
Chemiluminescent Microparticle Immunoassay
CPT Code:
80195