The monitoring of immunosuppressive drugs is an integral part of patient care after organ transplantation. Despite the availability of sensitive and highly pecific LCMS methods, immunoassays are still the most widely used methodology for monitoring these drugs. This is due to the extensive cost for LCMS instruments, the ease of use of immunoassays and their lower use of human resources as compared to LCMS. However, there are a number of pitfalls and limitations to the use of immunoassays. In particular standardization, specificity, cross-reactivity with metabolites, sensitivity, accuracy and precision are issues when monitoring different immunosuppressants such as cyclosporine, tacrolimus, sirolimus, everolimus and mycophenolic Acid (MPA). Meanwhile a number of different assays with different performance characteristics are available for the various compounds. Benefits and problems of the various assays will be discussed and compared to LCMS.
Clinical consequences associated with the use of immunoassays, such as potential under dosing due to metabolite cross reactivity, will also be discussed.

Keywords: otogenic intracranial complications, Organ Transplantation, skull bone defects