Performance of a no-pretreatment tacrolimus assay on the Dade Behring Dimension RxL clinical chemistry analyzer.

Abstract Background Therapeutic drug monitoring for tacrolimus is important for organ transplant patients receiving this immunosuppressant. Current available assays for tacrolimus require sample pre-treatment and operate in a batch mode. Here a no-pretreatment tacrolimus assay, performed on the Dade Behring Dimension analyzer is compared to the Abbott IMx tacrolimus assay and to an LC/MS/MS method. Methods Whole blood samples from 2 medical centers and different transplant types (kidney n  = 104, liver n  = 84, heart n  = 28, pancreas n  = 16, bone marrow n  = 11, lung n  = 7), were obtained and tacrolimus quantified by each of the 3 assays. Results The lower limit of the linear range was 1.2 ng/ml on the Dimension assay. Total imprecision was 9.8% and within-run imprecision was 9.6% at a tacrolimus concentration of 3.4 ng/dL. Passing–Bablock regression analysis determined the following relationships: DIMN = (1.16) LC/MS — 0.43, r  = 0.90 and DIMN = (0.99)IMx — 0.35, r  = 0.87. Conclusions The Dade Behring Dimension II Tacrolimus assay has adequate imprecision and correlates well with the reference method of LC/MS/MS. The assay appears suitable for clinical use, and has the advantages of not requiring a pretreatment step and the ability to be performed in a random-access mode.