Evaluation of a microparticle enzyme immunoassay for the measurement of sirolimus in whole blood (Abbott IMx sirolimus).

An immunoassay of sirolimus based on the microparticle enzyme immunoassay (MEIA) principle was evaluated on 105 whole blood samples (EDTA) drawn from a population of renal (n = 38) and hepatic or heart (n = 3) transplant patients. Each blood sample was analyzed simultaneously by MEIA and by a liquid chromatography mass spectrometry (LC-MS) method. The statistical analysis according to Passing-Bablok (x= LCMS, y= mean of two measurements of the same samples on IMx) produced the following results: Spearman r value = 0.9651, y(MEIA) = 0.99x (LCMS) - 0.26 microg/l. The analytical performance of the MEIA method showed a CV < or = 10% and a lower limit of quantification of 1.5 microg/l, which are acceptable for routine clinical monitoring. In conclusion, the MEIA method has shown robust, stable and reproducible features with an excellent correlation with the LC-MS method.