Background: There is significant immunoassay cross-reactivity between everolimus and sirolimus, and their routine determination using a common method may reduce the reagent costs.
Methods: In 122 blood samples from kidney (n = 30) and liver (n = 92) transplant recipients, everolimus concentrations were determined using the Abbott IMx® microparticle enzyme immunoassay (MEIA) as previously described, and the Abbott sirolimus chemiluminescence magnetic microparticle immunoassay (CMIA) on the Architect-i1000® system.
Results: A high correlation coefficient (r = 0.981, p < 0.001) and a linear regression MEIA = 0.73CMIA + 0.55, with an acceptable standard error of the estimate (ma68 = 0.32 ng/mL), were obtained, indicating the transferability of the results produced by both immunoassays.
Conclusions: The newly-developed sirolimus CMIA assay on the Architect® platform may be a valid alternative to other immunoassays for the routine therapeutic monitoring of everolimus.