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Updated: Jul 16, 2025
Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
Is the automated Elecsys tacrolimus assay on the Roche cobas e 602 analyzer an acceptable replacement for a liquid
Anastasia Gant Kanegusuku1, Kiang-Teck J Yeo1,2
1Department of Pathology, University of Chicago, Chicago, IL, US.
Objectives:
This study evaluated the suitability and accuracy of the automated Roche Elecsys tacrolimus electrochemiluminescence immunoassay (ECLIA) by comparing it with a current laboratory-developed test by liquid chromatography-tandem mass spectrometry (LC-MS/MS).
Methods:
The tacrolimus ECLIA was evaluated for precision, linearity, interference, and postextraction stability. Accuracy was compared with LC-MS/MS.
Results:
The tacrolimus ECLIA assay is precise, exhibits a measuring range of 0.75 to 30 ng/mL, and is tolerant of significant interferences (plasma indices: hemolysis <2306, icterus <55, lipemia <1427, and biotin <1200 ng/mL). Comparison with LC-MS/MS revealed a 26% proportional bias in patient samples evaluated for tacrolimus concentration (y = 1.26x + 0.08; r2 = 0.97; Sy/x = 0.94; n = 43) and an absolute mean (SD) bias of 2.2 (1.7) ng/mL. Postextraction studies confirmed that samples were stable for up to 30 minutes under routine laboratory conditions.
Conclusions:
The 2 major challenges for implementation of the tacrolimus ECLIA assay are the postextraction sample stability and the significant proportional bias observed compared with the LC-MS/MS reference method. The 30-minute window for analysis of extracted samples is a practical challenge to the routine workflow of the core laboratory. In addition, disagreement between the immunoassay and LC-MS/MS methods can lead to discordant clinical interpretations and ultimately affect patient care.
