title: Determination of everolimus in whole blood using the Abbott IMx sirolimus microparticle enzyme immunoassay.
abstract: OBJECTIVE
  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.
  
  
  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.
authors.affiliation: Unidad Monitorización Fármacos, Laboratorio Central, Hospital Clínico Universitario, Santiago de Compostela, Spain.
authors.forename: Lorena
authors.initials: L
authors.lastname: Bouzas
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Tutor
mesh_terms: D003429:Cross Reactions; D000068338:Everolimus; D016231:Fluorescence Polarization Immunoassay; D006801:Humans; D007124:Immunoenzyme Techniques / Q000379:methods*; D011933:Reagent Kits, Diagnostic; D012044:Regression Analysis; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000097:blood*
chemical_list: D011933:Reagent Kits, Diagnostic; D000068338:Everolimus; D020123:Sirolimus