Background: Sirolimus (Rapamune, Wyeth-Ayerst, Princeton, USA), is a macrolide antibiotic inhibitor of mammalian target of rapamycin (mTOR-i) with antiproliferative and immunosuppressant properties. This drug has a narrow therapeutic index and individual farmacokinetic variability requiring blood monitoring. The HPLC-MS is the referring method for blood sirolimus assay although immunoassay systems are widely used in therapeutic drugs monitoring. In this study we compare the sirolimus determinations using the Microparticle Enzyme Immunoassay (MEIA) run on the IMx analyser (Abbott) with the recently introduced Affinity Column- Mediated Immunoassay (ACMIA), run on the Dimension Xpand (Siemens Corporation, Deerfield,USA). Aim of our study was to evaluate the performance of ACMIA method, that has the advantage of not requiring pre-treatment procedure, compared to the MEIA method
