An illustration of the clinical relevance of detecting human antimouse antibody interference by affinity chromatography

Elevated Cancer antigen 125 (CA 125) serum concentrations (up to 221 kU/l) were measured in a 39 year old woman with a positive family history of brea st cancer. The serum determinations were performed with the automated Immul ite OM-MA chemiluminescent enzyme immunoassay system (Diagnostic Products). Laparoscopic evaluation of the ovaries did not reveal any abnormalities. C A 125 measurements in the same patient using the automated IMx immunoassay system (Abbott) demonstrated normal serum levels. Using a previously report ed chromatography procedure IgG type human antimouse antibody activity was found to be present in the serum samples explaining the falsely elevated le vels. To prevent this interference the manufacturer modified the assay syst em by replacing the monoclonal M11 detection antibody with a rabbit polyclo nal antibody. Using the modified OM-MA CA 125 assay results were comparable with the IMx values. (C) 1999 Elsevier Science Ireland Ltd. All rights res erved.