Noncompetitive enzyme immunoassay for carcinoembryonic antigen by flow injection chemiluminescence

Recently, many automated immunoassay analyzers have been developed for carcinoembryonic antigen (CEA) to overcome the shortcomings in traditional immunoassay methods that are time-consuming and labor-intensive. Flow injection immunoassay (FIIA) has been increasingly applied to laboratory medicine due to its ease in automation, rapid speed and reproducible results. It is important to develop a FIIA method for CEA determination.

Based on a noncompetitive immunoassay format, a CEA-immobilized immunoaffinity column inserted in the flow system was used to trap the unbound horseradish peroxidase (HRP)-labeled antibody after an off-line incubation of CEA and HRP-labeled anti-CEA. The trapped enzyme conjugate was detected by injecting substrates to produce an enhanced chemiluminescence (CL).

The linear range for CEA was 1.0-25 ng/ml with a correlation coefficient of 0.997 and a detection limit of 0.5 ng/ml. The sampling and chemiluminescence detection time for one sample was 5 min after a preincubation procedure of 25 min. Twenty five human serum samples detected by this method were in good agreement with the results obtained by immunoradiometric assay (IRMA).

This method could be used for rapid analysis of CEA and potentially other antigens.