Whole blood cyclosporin monitoring in liver and heart transplant patients: evaluation of the specificity of a fluorescence polarization immunoassay and an enzyme-multiplied immunoassay technique.

The specificity of two cyclosporin immunoassays were evaluated. Eleven patients were followed for the first four weeks after heart (n = 3) or liver (n = 8) transplantation. Cyclosporin A (CsA) monitoring was performed concomitantly by a monoclonal fluorescence polarization immunoassay (mFPIA) and enzyme-multiplied immunoassay technique (EMIT) during this period. For several patients, cyclosporin monitoring was also performed by high performance liquid chromatography (HPLC) or by polyclonal fluorescence polarization immunoassay (pFPIA). Liver function was assessed by follow-up of plasma total bilirubin, gamma-glutamyl transferase and alkaline phosphatase and renal function by plasma creatinine. All the patients presented episodes of impaired liver function. Higher CsA levels were found using mFPIA measurements as compared to the EMIT measurements (ratio mFPIA:EMIT (medium range) = 1.4 (1.0-2.3)). A higher degree of cross-reactivity of the antibody used in the mFPIA as compared to the EMIT was demonstrated by specific measurements of CsA and its primary metabolite, AM1, by HPLC.