ARUP's Laboratory Test Directory

Sirolimus by Tandem Mass Spectrometry : 0098467

Mnemonic: RAPAMUNE

Methodology: Quantitative High Performance Liquid Chromatography-Tandem Mass Spectrometry
Performed: Sun-Sat
Reported: Within 24 hours
Specimen Required: Patient Prep: Pre-dose (trough) levels should be drawn.

Collect: Lavender (EDTA) or pink (K2EDTA).

Specimen Preparation: Transport 1 mL whole blood. (Min: 0.25 mL)

Storage/Transport Temperature: Refrigerated.

Unacceptable Conditions: Serum or plasma. Specimens left at room temperature for longer than 24 hours. Clotted specimens.

Stability (collection to initiation of testing): Ambient: 24 hours; Refrigerated: 1 week; Frozen: 2 months
Interpretive Data: A therapeutic range of 4-12 ng/mL is proposed, based on a pre-dose (trough) steady-state specimen, concomitant cyclosporine, for a kidney transplant patient in the maintenance phase of therapy. A range of 12-20 ng/mL has been suggested for liver transplant. The range may vary with other transplant organs, when used in combination with drugs other than cyclosporine (or sirolimus alone), with the approach of the transplant center, and with other factors.  Symptoms of toxicity are more likely at predose (trough) concentrations that exceed 25 ng/mL. 
Note: Sirolimus (Rapamune®) whole blood concentrations can be measured by either chromatographic or immunoassay methodologies.  These two methodologies are not directly interchangeable and the measured sirolimus whole blood concentration is depended on the type of assay used.  References ranges may vary according to the specific immunoassay or LC/MS/MS test used. Generally, immunoassays have been reported to have a positive bias relative to the reference assay, HPLC with detection by tandem mass spectrometry (LC/MS/MS), due to detection of antibody cross-reactivity with sirolimus metabolites.
CPT Code(s): 80195
Cross References: Rapamune® (Sirolimus by Tandem Mass Spectrometry) , Rapamycin (Sirolimus by Tandem Mass Spectrometry)