Epitope group specificity of six immunoassays for carcinoembryonic antigen.

We have mapped the epitope group specificity of the monoclonal antibodies employed in six commercial sandwich immunometric assays for carcinoembryonic antigen (CEA), using cross-inhibition experiments with monoclonal antibodies previously classified in an International Workshop on the Epitope Reactivity of Monoclonal Antibodies against CEA. In this workshop it was shown that most monoclonal antibodies could be classified into one of five epitope groups, designated Gold groups 1-5. We found that of the six assay kits tested, five used solid-phase antibody of Gold group 4. Three of these (CIS ELSA 2-CEA, Hybritech Tandem-R CEA, Roche CEA EIA Duomab 60) used labeled antibody of Gold group 1, the remaining two (Abbott CEA-RIA Monoclonal, Wallac/LKB DELFIA CEA) used antibodies of Gold group 5. The sixth assay kit (Behringwerke Enzygnost CEA) used a solid-phase antibody of Gold group 1, and a polyclonal labeled antibody.