Issn Print: 0163-4356
Publication Date: 2005/04/01
Evaluation Of A Fluorescent Polarization Immunoassay (Fpia) For Whole Blood Everolimus Determination In Renal Transplant Recipients: 158
Paul Salm; Christopher Warnholtz; Jared Boyd; Lili Arabshahi; Peter Marbach; Paul Taylor
+ Author Information
Author Information: Australian Bioanalytical Services Pty Ltd, Princess Alexandra Hospital, Brisbane, Australia,
Excerpt
Everolimus is a macrocyclic lactone, which in combination with cyclosporine, has been shown to have synergistic immunosuppressive effects. The current methods available for everolimus analysis are based on HPLC-mass spectrometry techniques. To facilitate the routine monitoring of this drug, a new semi-automated immunoassay (Innofluor® Certican® Assay System) has been developed (Seradyn Inc, IN, USA) using FPIA technology on the TDx® and TDxFLx® instruments (Abbott Diagnostics, IL, USA). In this study we evaluated the FPIA (1) against our reported HPLC-tandem mass spectrometry (LC-MS) method (2). The inaccuracy and imprecision was assessed using batch dependent control samples at low (3.85, 4.56 μg/L), medium(11.30, 12.23 μg/L) and high (25.36, 25.59 μg/L) concentrations. A total of 333 pre- dose samples from 45 renal transplant recipients, collected up to 12 months post transplant and receiving chronic oral dosing of Certican® were analyzed by both methods. The inter-batch inaccuracy and imprecision of the FPIA for control samples (n = 34), was ≤ ± 6% and ≤13%, respectively. The cross validation of FPIA with LC-MS results yielded the least squares regression equation FPIA = 1.08(LC-MS) + 1.27 (r = 0.916, Sy/x = 1.44). The mean bias ± S.D. was 24.4 ± 18.2%. The FPIA had acceptable analytical performance over the range 4-25 μg/L. The higher values for FPIA everolimus results compared to LC-MS is possibly due to the cross-reactivity of the FPIA antibody with everolimus metabolites. This study suggests that FPIA is suitable for the therapeutic drug monitoring of everolimus in renal transplant patients. Further cross validation studies would help confirm inter laboratory robustness and reproducibility of the FPIA based on other renal transplant populations.
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