Preparation and characterization of digoxin antibody and its application to immunoassays: comparison of performance characteristics between enzyme immunoassay and immunostrip test

After characterizing digoxin immunogens and antibodies, we investigated the assay performances of enzyme immunoassay (ELA), biotin-streptavidin mediat ed enzyme immunoassay (B-Av EIA), and immunostrip test and compared the eff ectiveness of these tests fur detecting the presence of digoxin and its ana logues. The clinical use of digoxin is very complicated due to its narrow t herapeutic range. Thus, the development of a rapid and simple detection dev ice has been needed. In our study, we determined digoxin levels by EIA and B-Av ELA, and compared these tests with the immunotest strip to determine t he possibility of personal monitoring at the bedside. Three kinds of digoxi n antibodies were produced from various digoxin-BSA immunogens (digoxin/BSA molar ratio of 15:1, 50:1, and 200:1 in their preparation step). The antib odies produced were purified by the immunoaffinity chromatography using dig oxin-KLH or digoxin-BSA as the affinity ligand. Antibody #7 and its matchin g coating ligand of digoxin-KLH were selected by titration and sensitivity studies for use in ELA and B-AV ELA. Colloidal gold-labeled antibody #7 on a glass fiber membrane and digoxin-BSA on a nitrocellulose membrane were se lected for the immunostrip preparation. The EIA and B-Av EIA could detect 0 .01 ppb digoxin within 2.5 h, but the immunostrip could detect 0.01 ppm wit hin 3 min, which was three orders less sensitive than EIA or B-AV EIA. (C) 2000 Elsevier Science B.V. All rights reserved.