MAGLUMI Tacrolimus (CLIA) assay: analytical performances and comparison with LC-MS/MS and ARCHITECT Tacrolimus (CMIA) assay.

Objectives: Tacrolimus has been a cornerstone of immunosuppressive therapy over the past two decades. Due to its narrow therapeutic window and pharmacokinetic variability, drug monitoring is vital for enhancing the efficacy and safety during therapy. In the present study, we evaluated the analytical performances of the MAGLUMI Tacrolimus assay based on chemiluminescent immunoassay (CLIA), and compared with LC-MS/MS and the previously validated ARCHITECT Tacrolimus assay based on chemiluminescent microparticle immunoassay (CMIA).

Methods: We assessed the precision, limit of blank (LoB), limit of quantification (LoQ), limit of detection (LoD) and linearity of the MAGLUMI Tacrolimus assay using patient whole blood samples. Interference was assessed by introducing potential interferents into clinical samples. We also analyzed the correlation and agreement with the gold standard method (LC-MS/MS) and another previously validated high-performing ARCHITECT Tacrolimus (CMIA) assay by including 125 whole blood samples from patients and 44 spiked samples.

Results: MAGLUMI Tacrolimus (CLIA) assay exhibits superior precision, as coefficients of variation (CVs) for reproducibility and between-run precision were 0.55-3.63 % and 2.18-5.14 %, respectively. The LoB and LoQ were 0.1 μg/L and 0.5 μg/L. All samples in LoD verification had tacrolimus concentrations above LoB. The assay exhibited excellent linearity (=0.99990, 0.5-50 μg/L) with no interference. Additionally, the results of the MAGLUMI Tacrolimus (CLIA) assay showed strong correlation and concordance with LC-MS/MS and the CMIA assay.

Conclusions: The MAGLUMI Tacrolimus (CLIA) assay has excellent performance and strong concordance with LC-MS/MS and the ARCHITECT assay, making it a good alternative for tacrolimus measurement.