Therapeutic drug monitoring 2017 01 24() doi 10.1097/FTD.0000000000000376
Therapeutic drug monitoring (TDM) is recommended to guide therapy with the immunosuppressant Everolimus (EVL) in solid organ transplantation to prevent rejections and to limit toxicity. For TDM, pre-dose EVL concentrations are measured in whole blood mainly by liquid chromatography tandem mass spectrometry (LC-MS/MS). In addition, two immunoassays (QMS® Everolimus and Elecsys® Everolimus) are commercially available. The aim of this study was to evaluate the comparability of EVL results determined with the two immunoassays and a validated LC-MS/MS test using samples from kidney (KT)-liver (LT)- and heart (HT) transplant recipients.
Analysis of pre-dose samples from KT (n = 56), LT (n = 60), and HT (n = 59) recipients, obtained at variable time points post-transplantation, was performed by LC-MS/MS and with the two immunoassays. The QMS® Everolimus assay was applied on Dimension® Xpand Plus and the Elecsys® Everolimus assay on cobas e 411 analyzer. Results were compared by the Spearman’s rank correlation coefficient, unbiased Passing&Bablok linear regression test, and Bland-Altman plot.
Results generated with both immunoassays correlated well with those of LC-MS/MS. An overestimation of EVL concentrations by the Elecsys® Everolimus compared to LC-MS/MS was observed (mean bias: 34.2%). Using the QMS® Everolimus, a small but significant negative deviation (mean bias: -8.0%) was found. Looking at KT, HT, and LT samples separately, the bias to LC-MS/MS seen with the Elecsys® Everolimus was similar. With the QMS® Everolimus, the best agreement was observed with the KT samples followed by LT and HT.
Results generated by the three methods are not consistent regarding their diagnostic value. Both laboratories and manufacturers should take care to inform their costumers about the between-method differences to avoid misinterpretation of the results in clinical practice.