Performance Evaluation of Affinity Column Mediated Immunometric Assay for Tacrolimus

Abstract

Background : Therapeutic drug monitoring (TDM) of tacrolimus is essential because of narrow therapeutic range and poor correlation of dose to blood concentration. Affinity Column Mediated Immunometric Assay (ACMIA) does not require a pretreatment steps in measurement of tacrolimus. In this study, we evaluated the performance of tacrolimus assay using ACMIA (Dimension RxL Max, Dade Behring). Methods : The imprecision, the linearity and the detection limits and the interferences by bilirubin and chyle, and correlation with hematocrit for tacrolimus by ACMIA were evaluated according to Clinical and Laboratory Standards Institute guidelines EP5-A2, EP6-A, EP17-A, EP9-A2, and EP7-A2. Method comparison studies with microparticle enzyme immunoassay (MEIA) (IMx Tacrolimus 11, Abbott Laboratories) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) (Waters 2795 Quattromicro API, Micromass) were also performed. Results: The total imprecision for low, middle and high level was 12.8%, 9.0% and 6.7%, respectively. The range of tacrolimus from 3.1 ng/mL to 35.4 ng/mL showed a clinically relevant linearity. The limit of detection and the functional sensitivity were 0.24 ng/mL and 0.72 ng/mL, respectively. Tacrolimus concentration measurement (Tac-CM) with ACMIA did not show significant interferences with bile and chyle and also did not show significant correlation with hematocrit. In comparison study for Tac-CM with MEIA and LC-MS/MS, Tac-CM with ACMIA showed a good correlation with MEIA (r=0.950) and LC-MS/MS (r=0.946). Conclusions : The imprecision, linearity, detection limits, interference and correlation of Tac-CM with ACMIA were suitable for clinical use. Tac-CM with ACMIA could reduce turn around time and help clinicians to manage transplant patients on immunosuppressant therapy. (Korean J Lab Med 2009;29:415-22)