Comparison of the CEDIA^® and MEIA^® assays for measurement of tacrolimus in organ transplant recipients

Objectives: Tacrolimus is widely used in organ transplantation. We evaluated 2 immunoassays, CEDIA^® and MEIA^®, for the measurement of whole blood tacrolimus concentrations. Methods: For each assay the following were evaluated: total precision, limit of detection (analytical sensitivity), limit of quantitation (functional sensitivity), linearity, and accuracy. Patient correlation studies were performed, comparing each assay with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Results: Total precision for MEIA, corresponding to mean concentrations of 6.8 and 22.5 ng/ml, was 17.4 and 11.9%, respectively. The limit of detection was 0.9 ng/ml, and the limit of quantitation was 4.7 ng/ml. Total precision for CEDIA, corresponding to mean concentrations of 5.3 and 19.9 ng/ml, was 20.6 and 6.3%, respectively. The limit of detection was 0.8 ng/ml, with a limit of quantitation of 4.9 ng/ml. Analysis of proficiency material demonstrated acceptable performance for both assays. In addition, both assays were acceptably linear over their respective reportable ranges. Analysis of patient correlation data using Passing-Bablok analysis and Bland-Altman plots demonstrated a positive average bias for both assays versus LC-MS/MS results. Conclusion: Based on our evaluation, both assays demonstrated acceptable performance for use in clinical monitoring of tacrolimus.