Lorena Bouzas1, J Carlos Tutor. 1. Unidad Monitorización Fármacos, Laboratorio Central, Hospital Clínico Universitario, Santiago de Compostela, Spain.
Abstract
OBJECTIVES: Everolimus (Certican) is a new immunosuppressant derived from sirolimus (Rapamune) with a 2-hydroxyethyl chain at position 40 of the macrolide ring. The aim of our study was to evaluate the possible determination of everolimus in whole blood using a commercialized microparticle enzyme immunoassay for sirolimus determination. DESIGN AND METHODS: Everolimus concentrations were determined in blood samples from 11 kidney transplant patients (n=51) and different control materials (n=35) using the Seradyn Innofluor Certican fluorescence polarization immunoassay (FPIA) and the Abbott IMx sirolimus microparticle enzyme immunoassay (MEIA). RESULTS: The MEIA gave a concentration-dependent cross-reactivity with the everolimus, with a linear regression between the assigned values (y) for the Innofluor Certican calibrators and those obtained (x) using this immunoassay: y=0.96x+0.67 (ma68=0.21 microg/L, r=0.974, p<0.001). The within- and between-run coefficients of variation using the MEIA were <or=7.3%. In analyzing the different blood samples from patients and control materials using the MEIA and FPIA, a linear regression was found: MEIA=0.99FPIA-0.46 (ma68=0.32 microg/L, r=0.967, p<0.001). Correcting the MEIA results by means of the linear regression equation found between the assigned values for the Innofluor Certican calibrators and those obtained using this immunoassay led to a reduction in the deviation with respect to the FPIA values. The possible effect of the hematocrit on the results is analogous for both immunoassays. CONCLUSIONS: The Abbott IMx sirolimus MEIA permits the simple and precise determination of everolimus in whole blood, making it a valid alternative for the therapeutic monitoring of this immunosuppressant agent.
OBJECTIVES:Everolimus (Certican) is a new immunosuppressant derived from sirolimus (Rapamune) with a 2-hydroxyethyl chain at position 40 of the macrolide ring. The aim of our study was to evaluate the possible determination of everolimus in whole blood using a commercialized microparticle enzyme immunoassay for sirolimus determination. DESIGN AND METHODS: Everolimus concentrations were determined in blood samples from 11 kidney transplant patients (n=51) and different control materials (n=35) using the Seradyn Innofluor Certican fluorescence polarization immunoassay (FPIA) and the Abbott IMx sirolimus microparticle enzyme immunoassay (MEIA). RESULTS: The MEIA gave a concentration-dependent cross-reactivity with the everolimus, with a linear regression between the assigned values (y) for the Innofluor Certican calibrators and those obtained (x) using this immunoassay: y=0.96x+0.67 (ma68=0.21 microg/L, r=0.974, p<0.001). The within- and between-run coefficients of variation using the MEIA were <or=7.3%. In analyzing the different blood samples from patients and control materials using the MEIA and FPIA, a linear regression was found: MEIA=0.99FPIA-0.46 (ma68=0.32 microg/L, r=0.967, p<0.001). Correcting the MEIA results by means of the linear regression equation found between the assigned values for the Innofluor Certican calibrators and those obtained using this immunoassay led to a reduction in the deviation with respect to the FPIA values. The possible effect of the hematocrit on the results is analogous for both immunoassays. CONCLUSIONS: The Abbott IMx sirolimus MEIA permits the simple and precise determination of everolimus in whole blood, making it a valid alternative for the therapeutic monitoring of this immunosuppressant agent.