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Objective】Five current immunoassay methods (chemiluminescent enzyme immunoassay [CLIA], affinity column mediated immune assay [ACMIA], enzyme multiplied immunoassay technique [EMIT], electro-chemi luminescence immunoassay [ECLIA], and enzyme-linked immunosorbent assay [ELISA]) in Japan were used there to monitor tacrolimus concentrations in the whole blood. The aim of this study was to assess interhospital laboratory variability (coefficient of variation: CV) for each of the 5 methods, the comparability of control samples, and the results obtained by immunoassay measurements (accuracy).
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Design and Methods】A total of 100 laboratories routinely performing therapeutic drug monitoring (TDM) of tacrolimus participated. Reports of 67, 19, 8, 5, and 1 laboratories reported showed results using, respectively, CLIA, ACMIA, EMIT, ECLIA, and ELISA merhods for the tacrolimus assay. In iMPT2014, four spiked samples (0, mean 1.7, 4.8, and 14.4 ng/ml for LC-MS) were sent to each hospital.
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Results】CVs for CLIA, ACMIA, EMIT, and ECLIA assays at a concentration of 4.8 and 14.4 ng/ml were less than 18.3%. Especially, CV values at 1.7 ng/ml for ECLIA were 8.9%. Accuracies for the EMIT assay at a concentration range of 1.7―14.4 ng/ml were 24.8% to 31.2%, whereas those for CLIA, ACMIA, and ECLIA were within ±16.9% at the same concentration range.
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Conclusion】The interlaboratory mean CVs at a target concentration of 5 ng/ml ranging from 6.8% to 18.3%, according to the immunoassay method. Higher interlaboratory variability mainly depends on the difference between analytical methods. Clinicians need to understand the precision and accuracy of using a tacrolimus assay well and should carry out a TDM.
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