Performance characteristics of a no-pretreatment, random access sirolimus assay for the Dimension® RxL clinical chemistry system

ObjectivesCurrent therapeutic drug monitoring methods for sirolimus require a manual pre-treatment step and batch analysis. We describe and validate a no-pretreatment, random access sirolimus assay for the Dimension® RxL clinical chemistry system from Siemens Healthcare Diagnostics Inc.Design and methodsWhole blood samples from renal transplant patients prescribed sirolimus were analyzed by the LC–MS/MS reference method, Abbott IMx and Dimension RxL methods in accordance with CLSI recommendations.ResultsThe Dimension sirolimus assay had a functional sensitivity of 2.0 ng/mL and repeatability and within-laboratory imprecision less than 12.6% at 3 ng/mL and less than 5% at 11–12 ng/mL. Least squares linear regression demonstrated the following relationships: RxL = 1.20(LC–MS/MS) – 0.70, r = 0.95 and RxL = 1.33(IMx) – 0.75, r = 0.96.ConclusionsThe Dimension sirolimus assay correlates well with the LC–MS/MS reference and IMx immunoassay methods and has the advantage of random access analysis without a manual pre-treatment step.