Comparative Analyses of Cyclosporine in Whole Blood and Plasma by Radioirmmunoassay, Fluorescence Polarization Immunoassay, and High-Performance Liquid Chromatography

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Abstract
Cyclosporine (CsA) concentrations were prospectively monitored for 6 months after transplantation in 66 consecutive renal transplant recipients. Analysis for CsA was performed with polyclonal radioimmunoassay (RIA), high-performance liquid chromatography (HPLC), and fluorescence polarization immunoassay (FPIA) in whole blood and plasma, and with specific and nonspecific monoclonal RIA in whole blood. Precision within and between runs was best with FPIA, followed by HPLC and RIA. A strong correlation was observed between the results obtained with HPLC and specific monoclonal RIA (r = 0.98). Correlation coefficients between the other assays ranged from 0.56 (plasma HPLC versus blood polyclonal RIA) to 0.91 (blood nonspecific monoclonal RIA versus blood FPIA). The highest values for CsA concentrations in blood were found with nonspecific monoclonal RIA, followed by FPIA and polyclonal RIA (mean ratio versus specific monoclonal RIA was 3.3, 2.9, and 2.4, respectively). Specific monoclonal RIA had 7% higher values than HPLC. There was a more than threefold interindividual variation in the mean ratio between specifically and nonspecifically measured CsA concentrations in whole blood and plasma. The ratio between CsA concentrations, determined with specific versus nonspecific methods in whole blood, decreased significantly during the first month after transplantation (from 0.42 to 0.35, as assayed with specific monoclonal RIA versus polyclonal RIA in whole blood; p < 0.05). The concentrations in blood were, on the average, three times higher than those in plasma, althouth there was a more than fourfold interindividual variation in the mean values. The large interindividual variations in ratios between the results obtained in different assays and in different media show that each procedure for monitoring of CsA in transplant patients has to be evaluated separately. Moreover, specific analytical methods should be used for monitoring CsA.