Analytical performance of QMS everolimus assay on ortho vitros 5,1 FS fusion analyzer: Measuring everolimus trough levels for solid organ transplant recipients

BACKGROUND:: Everolimus has recently been approved by Food and Drug Administration for graft maintenance in liver transplant recipients. This drug has a narrow therapeutic index and benefits from close blood level monitoring. Currently, in the United States, the Thermo Fisher Scientific Quantitative Microsphere System (QMS) Everolimus Immunoassay is the only Food and Drug Administration-cleared immunoassay for monitoring everolimus in renal transplant recipients. However, studies on this assay adapted to the Ortho Vitros 5,1 FS chemistry analyzer have not been published, and data of this assay applied to monitoring drug levels in liver transplant recipients are limited. Here, the authors evaluated and validated the QMS everolimus assay on the Vitros analyzer and its application to supporting the immunosuppressant management of mainly liver transplant recipients. METHODS:: The analysis was performed according to the QMS assay package insert. The method was compared with a liquid chromatography-tandem mass spectrometry method from a reference laboratory using a total of 34 samples from 1 double lung and liver, 8 liver, and 3 kidney recipients. The method comparison was assessed by Deming regression. Proficiency test materials issued by Everolimus TDM Proficiency Support Program were tested and compared with the peer group results of using the QMS kits. RESULTS:: The assay was linear in the range of 0.75-20.0 ng/mL. Limit of detection was 0.70 ng/mL and lower limit of quantitation was 0.75 ng/mL. Within-day and between-day (20 days) coefficients of variation were between 3.1% and 16.5% at mean levels of 5.3, 12.0, and 17.2 ng/mL, respectively. We obtained a Deming regression of y = 1.271 - 0.666 (r = 0.880) when comparing with the liquid chromatography- tandem mass spectrometry method. CONCLUSIONS:: The authors concluded that the analytical performance of the QMS everolimus immunoassay by the Vitros 5,1 FS analyzer was satisfactory for monitoring drug levels of solid organ transplant patients.