title: Evaluation of 2 immunoassays for monitoring low blood levels of tacrolimus.
abstract: The objective of this study was to evaluate the analytical performance of 2 new tacrolimus immunoassays (Dade Dimension Xpand and Abbott ARCHITECT) for therapeutic drug monitoring as possible replacements for the current method in our laboratory, the Abbott IMx tacrolimus assay. Attending physicians at our institute desire to minimize calcineurin inhibitor therapy in kidney allograft recipients to prolong graft survival and improve the quality of life of their patients. Proposed future target trough levels of tacrolimus in whole blood are in the range of 2-4 ng/mL, which requires an assay with a limit of quantification (LOQ) below this range, ideally around 1 ng/mL (European Consensus Recommendation from the Committee on Tacrolimus Optimization). Method comparison analysis of the Dade and ARCHITECT assays showed good correlation to the IMx assay, with correlation coefficients of 0.94 and 0.96, respectively. Both assays reported tacrolimus concentrations lower on average than IMx as demonstrated by slopes of 0.83 (Dade) and 0.93 (ARCHITECT). LOQ for both Dade instruments tested was >4 ng/mL, whereas the LOQ for the ARCHITECT i2000 and i1000 instruments was 0.8 and 0.5 ng/mL, respectively (upper 95% confidence limit). Values reported from both Dade instruments were observed to shift over time, whereas the values on the IMx and ARCHITECT instruments were stable. The Abbott ARCHITECT Tacrolimus assay is a sensitive and precise assay that meets the new LOQ recommendation, 1 ng/mL, for monitoring tacrolimus in whole blood.
authors.affiliation: Iris and B. Gerald Cantor Clinical Research Laboratory, The Rogosin Institute, New York Presbyterian-Weill Cornell Medical Center, 310 E 67th Street, New York, NY 10065, USA.
authors.forename: Shawn
authors.initials: S
authors.lastname: Amann
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Parker
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Levine
mesh_terms: D016903:Drug Monitoring; D006801:Humans; D007118:Immunoassay; D007166:Immunosuppressive Agents / Q000097:blood*; D016559:Tacrolimus / Q000097:blood*
chemical_list: D007166:Immunosuppressive Agents; D016559:Tacrolimus