Therapeutic Drug Monitoring of Everolimus: Comparability of Concentrations Determined by 2 Immunoassays and a Liquid Chromatography Tandem Mass Spectrometry Method.

Background: Therapeutic drug monitoring is recommended to guide therapy with the immunosuppressant everolimus (EVL) in solid organ transplantation to prevent rejections and to limit toxicity. For therapeutic drug monitoring, predose EVL concentrations are measured in whole blood mainly by liquid chromatography tandem mass spectrometry (LC-MS/MS). In addition, 2 immunoassays [Quantitative Microsphere System (QMS) EVL and Elecsys EVL] are commercially available.