Accuracy evaluation of automated electrochemiluminescence immunoassay for everolimus and sirolimus compared to liquid chromatography‐tandem mass spectrometry

BACKGROUND: We evaluated the analytical performance of a newly developed electrochemiluminescence immunoassay for everolimus and sirolimus compared to that of liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). METHODS: According to Clinical and Laboratory Standards Institute guidelines, the analytical performance including precision, recovery, linearity, and carryover was evaluated. For correlation evaluation, the results of Elecsys(®) analysis of everolimus and sirolimus were compared with those of LC‐MS/MS using 120 samples from patients treated with everolimus or sirolimus. RESULTS: The within‐run and total imprecision values were as follows: 2.3%‐4.5% and 4.5%‐6.4% for the everolimus assay; 3.3%‐4.8% and 4.7%‐8.1% for the sirolimus assay, respectively. The measured concentration was linear over the range of 0.718‐27.585 ng/mL for everolimus analysis and 0.789‐26.880 ng/mL for sirolimus analysis (all R (2) > 0.99). Recovery was 93.5%‐105.5% for the everolimus assay and 99.2%‐109.1% for the sirolimus assay (except lowest levels). Carryover was −1.09% for the everolimus assay and −0.12% for the sirolimus assay. The results of the two chemiluminescence immunoassays showed acceptable correlations with those of LC‐MS/MS (R = 0.9585 and R = 0.9799, respectively). The two immunoassays showed slightly proportional biases compared to LC‐MS/MS. CONCLUSION: Elecsys(®) Everolimus and Sirolimus assays showed acceptable analytical performance in precision, linearity, and correlation compared to LC‐MS/MS These methods can be adopted in the clinical laboratory for rapid therapeutic drug monitoring of patients who require treatment with immunosuppressants.