Measurement of Cyclosporin-A Serum Levels in the Fluorescence Polarization Immunoassay and the Clinical Evaluation

Cyclosporin-A (CYA) serum levels have been monitored to prevent graft rejection and its toxicity in organ transplant recipients. In this study, we measured CYA serum levels by using the fluorescesnce polarization immunoassay (FPIA) method, and compared this new method with the conventional radioimmunoassay (RIA) method and the high-performance liquid chromatography (HPLC) method. The coefficient of correlation between the values obtained by the HPLC and RIA methods was 0.893 and that between the values obtained by the HPLC and FPIA methods was 0.911, while the values obtained by the RIA and FPIA methods correlated well with 0.906 of correlation. However, the value of the FPIA method was approximately 1.8-fold higher than that of the HPLC method.It is presumable that the antibody in the FPIA method cross-reacts with the metabolites of CYA. The recovery of the FPIA method was approximately 100 per cent, and the reproducibility was satisfactory. In conclusion, we expect the FPIA to be useful as a new method for the routine monitoring of drugs.