ABSTRACT
The aim of the study was to investigate the better accuracy of the 2-h post-dose (C2) levels of cyclosporine (CyA), compared with the pre-dose (C0) levels and to evaluate the results measured by a monoclonal or a polyclonal immunoassay. The parent compound of CyA in C2 (monoclonal2) was measured in 53 kidney transplant patients by the monoclonal fluorescence polarization method, as well as the parent compound plus metabolites (polyclonal2) by the polyclonal fluorescence polarization method. Also, the parent compound was measured in 21 of the patients for the C0 (monoclonal0), whereas the parent compound plus metabolites in 36, for the C0 (polyclonal0). As level of metabolites was considered the difference between polyclonal and monoclonal values (polyclonal-monoclonal), either in C0 (metabolites0) or in C2 (metabolites2). The ratio polyclonal2/monoclonal2 gave a mean value of 1.7+/-0.2 (mean+/-SD), whereas the mean value of the ratio polyclonal0/monoclonal0 was 2.3+/-0.6, with almost double variation. The mean value of the ratio metabolites2/monoclonal2 was 0.7+/-0.2 and of the ratio metabolites0/monoclonal0 was 1.3+/-0.6. The difference between the two ratios is very significant (p = 0.000001) and they are not correlated with each other (r = 0.18, p = 0.44). The measurements of monoclonal0 and polyclonal0 or monoclonal2 and polyclonal2 are very significantly correlated (r = 0.94, p = 0.000001 and r = 0.97, p = 0.000001, respectively). In C0 the proportion of metabolites is higher than in C2, with a double variation, as the degree of metabolism is diverse. Consecutively, in monoclonal methods, as cross-reactions occur with metabolites, it is more accurate to use the C2 measurement for the evaluation of CyA. The application of both methods, the polyclonal and the monoclonal, could be a useful tool as it gives an estimation of metabolites whose degree of contribution to the immunosuppressive result is difficult to ascertain. Finally, if for reasons of clinical experience, the polyclonal method is used, then the mean therapeutic levels of polyclonal2 are 1.5-1.7 compared with monoclonal2.
