Cyclosporine concentrations in blood after liver transplantation: correlation of immunoassay results with clinical events.

To investigate the clinical utility of immunoassays for cyclosporine and metabolites in plasma and whole blood, we monitored 25 patients after orthotopic liver transplantation. We compared cyclosporine as measured by TDx fluorescence polarization immunoassay (of both plasma and whole blood) and by two polyclonal radioimmunoassays (from Sandoz and INCSTAR). We found considerable differences in measured cyclosporine concentrations, which were dependent on method, matrix, and clinical condition. Correlation coefficients between results by the various methods for samples from individual patients ranged from 0.825 to 0.996. The three methods used for monitoring cyclosporine in whole blood gave proportional results (Sandoz less than INCSTAR less than TDx) in individual patients, but results for the two methods for plasma sometimes differed by more than 100%. In some cases, ratios of plasma cyclosporine concentration (result by TDx/result by Sandoz) were correlated with disturbances in hepatic excretory function or kidney function. This ratio may be useful in monitoring for nephrotoxicity.