Preliminary Analytical Verification of the Automated Cobas i601 LC-MS/MS System for Immunosuppressant Quantification in a Clinical Laboratory

Abstract

INTRODUCTION: Therapeutic drug monitoring (TDM) of immunosuppressive drugs is essential to maintain concentrations within narrow therapeutic windows and minimize toxicity. Automated LC–MS/MS platforms can combine the analytical specificity of mass spectrometry with workflow efficiency suitable for routine laboratories. OBJECTIVES: To preliminarily evaluate the analytical performance of the Cobas i601 automated LC–MS/MS system for quantifying tacrolimus, cyclosporine, everolimus, and sirolimus and to compare results with routine immunoassays and an LC–MS/MS method for sirolimus. METHODS: Imprecision, bias, and linearity were assessed according to the Clinical Laboratory Standards Institute (CLSI) EP10-A3 standard using quality-control materials. Method comparison and bias estimation versus the Dimension EXL 200 immunoassays and an LC–MS/MS technique for sirolimus followed the CLSI EP09-A3 standard. Regression analyses and predicted biases at therapeutic range concentrations were compared with allowable limits. RESULTS: The Cobas i601 showed good precision and linearity, meeting manufacturer specifications. The highest coefficients of variations for tacrolimus, everolimus, cyclosporine, and sirolimus were 4.0%, 4.7%, 3.6%, and 4.8%, and the maximum EP10-A3 biases were −7.4%, −3.9%, 4.7%, and 5.4%, respectively. In the method comparison, tacrolimus, everolimus, and cyclosporine showed substantial negative biases versus immunoassays (−22.7%, −38.9%, and −37.5%), exceeding allowable limits. Sirolimus exhibited smaller positive bias relative to the LC–MS/MS method (12.5%). Interchangeability between the methodologies cannot be assumed. CONCLUSION: The Cobas i601 provides reliable automated LC–MS/MS quantification of immunosuppressants, with good precision and linearity. Method-dependent biases highlight the need for careful interpretation during technology transitions. The Cobas i601 shows strong potential for routine LC–MS/MS implementation in TDM in clinical laboratories.