Performance and Specificity of Monoclonal Immunoassays for Cyclosporine Monitoring: How Specific Is Specific?
Background: Immunoassays designed for the selective measurement of cyclosporin A (CsA) inadvertently show cross-reactivity for CsA metabolites. The extent and clinical significance of the resulting overestimation is controversial. A comprehensive assessment of old and new methods in clinical specimens is needed. Methods: In a comprehensive evaluation, CsA was analyzed in 145 samples with the new CEDIA® assay and compared with the Emit® assay with the old and new pretreatments, the TDx® monoclonal and polyclonal assays, the AxSYM®, and HPLC. All samples were from patients with liver and/or kidney transplants. Results: The CEDIA offered the easiest handling, followed by the AxSYM, which showed the longest calibration stability. The TDx monoclonal assay provided the lowest detection limit and the lowest CVs. The mean differences compared with HPLC were as follows: Emit, 9 12%; CEDIA, 18%; AxSYM, 29%; and TDx monoclonal, 57%. The CycloTrac® RIA paralleled the Emit results. In contrast to t
