[Immunoanalytical methods of cyclosporine A determination]

The standard method for determination of CyA in blood is a good validated HPLC method. HPLC methods were developed which make it possible to determine not only the parent drug, but also the main metabolites of CyA: AMI (M17), AM9 (M1), and AM4N (M21). HPLC methods for determination of CyA are very laborious and expensive. Most transplantation centres in the world use immunoanalytical methods for TDM of CyA. In recent years there has been an increase in the number of users of nonisotopic automated methods (Abbott TDx mono, AxSYM, Dade-Behring EMIT or Microgenic Cedia), which render instantaneous analysis possible. The analysis of the results of CyA in the blood in patients after transplantation shows that all immunoanalytical methods overestimate the concentration of CyA against HPLC results. The usually presented series of results is as follows: HPLC < RIA = EMIT < CEDIA < AxSYM < TDx. The differences are difficult to explain only by a different degree of cross reactivity for particular metabolites of CyA with the antibody used in the immunoanalytical method. The criterion of IFCC, which should be met by each immunoanalytical method in order to be used for TDM of CyA, should be redrawn, because it is not able to ensure sufficient specificity of the method. A suitable, cheap, and quick analytical method for TDM of CyA is still wanted. Some transplantation centres, including ours, carry out not only one method for effective TDM of CyA.