Performance evaluation of a restored dimension TACR assay: An automated platform for measuring the whole blood tacrolimus concentration

Background: Monitoring tacrolimus levels is essential for successful organ transplantation. The Dimension TACR (Siemens Healthcare Diagnostics, USA) is an automated platform used to measure tacrolimus concentrations. Recently, the manufacturer started shipping an assay reagent with improved functions. We evaluated the analytical performance of the improved Dimension TACR assay. Methods: The precision was evaluated according to the CLSI EP5-A2 guideline. Two levels of control materials were analyzed twice a day in duplicate for 20 days in the precision study. The linearity was evaluated using five levels of mixed calibrators based on the CLSI EP6-A guideline. A comparison study was conducted based on the CLSI EP9-A3 guideline using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limit of blank (LoB), limit of detection (LoD), and limit of quantitation (LoQ) were evaluated using CLSI EP17-A2. Results: In the precision analyses, the within-run, between-run, and total coefficients of variation were 5.8%, 4.6%, and 8.1% for the low level control and 4.2%, 2.8%, and 5.9% for the high level, respectively. A linear range of 1.18 - 8.32 ng/mL was observed. In the comparison study, the correlation coefficient, slope, and intercept were 0.9768, 1.118, and -0.251, respectively. The results of the Dimension TACR assay were slightly higher than those of LC-MS/MS (mean bias 0.64 ng/mL). The LoB, LoD, and LoQ were 0.063 ng/mL, 0.408 ng/mL, and 1.15 ng/mL, respectively. Conclusions: The Dimension TACR assay showed good precision and linearity. Although the results using the Dimension TACR assay were higher than those using mass spectrometry, the differences were acceptable clinically.