COMPARISON OF 4 DIFFERENT CYCLOSPORINE IMMUNOASSAYS IN HEART AND KIDNEY-TRANSPLANT RECIPIENTS

Four different immunoassays were used to measure cyclosporine A (CsA) plasma (20°C) levels in heart and kidney transplant recipients. Two radioimmunoassays (RIAs) (Sandimmune and Cyclotrac) and the fluorescence polarization immunoassay (FPIA) were based on polyclonal antibodies, whereas the fourth (Cyclotrac-SP) used a CsA-specific mouse monoclonal antibody. We found considerable differences in measured CsA concentrations, which were dependent on the method used and the clinical situation of the patient. Correlation coefficients between the nonspecific assays ranged from 0.899 to 0.901 with plasma values increasing in the order Sandimmune < Cyclotrac < FPIA. In the CsA-specific RIA, values were lower, and the correlation with the nonspecific assays ranged from 0.761 to 0.795. In the first 21 days posttransplantation, the heart transplant group showed a higher ratio of nonspecific/specific CsA (mean 4.0) compared with the subsequent period (mean 2.3) or with renal transplant recipients (mean 2.4). The TDX method showed the best assay characteristics. In heart transplant patients with specific and nonspecific 125I-RIA methods, mean CsA levels were 25% lower during rejection periods compared with periods without signs of rejection. © 1990 Raven Press, Ltd.