Multicenter study of Abbott AxSYM® Digoxin II assay and comparison with 6 methods for susceptibility to digoxin-like immunoreactive factors

Abstract

Performance characteristics of the Abbott nonpretreatment AxSYM® Digoxin II assay were evaluated for quantification of digoxin at four independent sites. Correlation of digoxin measurements with the Abbott pretreatment AxSYM®, Baxter Stratus® II, Abbott TDx/TDxFLx II®, Abbott IMx®, Emit® 2000, and Beckman Synchron CX® digoxin assays showed acceptable agreement, as indicated by: slope values >0.84, r >0.90, y- intercepts for all comparisons at or below the assay detection limit, and S(y|x) ranging between 7.5% and 15.4% of the average digoxin value. Susceptibility to interference from digoxin-like immunoreactive factors (DLIFs) was examined in 233 samples from renal patients, liver disease patients, cord blood, and third-trimester pregnancies; the AxSYM Digoxin II assay demonstrated the least DLIFs interference DLIF susceptibility for four of the methods was significantly greater (P <0.05) than in the AxSYM Digoxin II assay; susceptibilities of the Stratus II and Emit 2000 methods were similar to the AxSYM Digoxin II assay.