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Updated: May 28, 2026
Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
The need for standardization of tacrolimus assays
Daniel M Levine1, Gregory T Maine, David A Armbruster
1Rogosin Institute, New York, NY, USA. dml9006@nyp.org
Background:
Owing to the lack of an internationally recognized tacrolimus reference material and reference method, current LC-MS and immunoassay test methods used to monitor tacrolimus concentrations in whole blood are not standardized. The aim of this study was to assess the need for tacrolimus assay standardization.
Methods:
We sent a blinded 40-member whole-blood tacrolimus proficiency panel (0-30 μg/L) to 22 clinical laboratories in 14 countries to be tested by the following assays: Abbott ARCHITECT (n = 17), LC-MS (n = 9), and Siemens Dade Dimension (n = 5). Selected LC-MS laboratories (n = 4) also received a common calibrator set. We compared test results to a validated LC-MS method. Four samples from the proficiency panel were assigned reference values by using exact-matching isotope-dilution mass spectrometr at LGC.
Results:
The range of CVs observed with the tacrolimus proficiency panel was as follows: LC-MS 11.4%-18.7%, ARCHITECT 3.9%-9.5%, and Siemens Dade 5.0%-48.1%. The range of historical within-site QC CVs obtained with the use of 3 control concentrations were as follows: LC-MS low 3.8%-10.7%, medium 2.0%-9.3%, high 2.3%-9.0%; ARCHITECT low 2.5%-9.5%, medium 2.5%-8.6%, high 2.9%-18.6%; and Siemens/Dade Dimension low 8.7%-23.0%, medium 7.6%-13.2%, high 4.4%-10.4%. Assay bias observed between the 4 LC-MS sites was not corrected by implementation of a common calibrator set.
Conclusions:
Tacrolimus assay standardization will be necessary to compare patient results between clinical laboratories. Improved assay accuracy is required to provide optimized drug dosing and consistent care across transplant centers globally.
