Evaluation of the CEDIA digoxin assay on Boehringer Mannheim/Hitachi 717 analyzer

Some aspects of a new homogeneous enzyme immunoassay for the determination of digoxin have been evaluated, as part of a multicenter project. The CEDIA Digoxin assay is based on the use of two beta-galactosidase fragments (EC 3.2.1.23) produced by recombinant DNA techniques, one of them linked to digoxin. These two fragments couple to form the complete active enzyme, if not hindered by anti-digoxin antibodies. Digoxin in serum competes for antibody binding. The procedure can easily be automated and does not require special equipment. The imprecision of the method was studied at three different concentration levels (0.56, 1.29 and 2.77 ng/mL of digoxin). Within-run coefficients of variation were 8.01%, 5.57% and 3.30%, respectively, the corresponding between-day CVs being 17.4%, 8.41% and 4.89%. The procedure was found to be linear up to 4.4 ng/mL. Reagents were stable for at least four weeks. Results obtained by the CEDIA Digoxin assay compared well with those obtained by fluorescence polarization immunoassay.