Noncompetitive enzyme immunoassay for carcinoembryonic antigen by flow injection chemiluminescence

BACKGROUND: 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. METHODS: 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). RESULTS: 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). CONCLUSIONS: This method could be used for rapid analysis of CEA and potentially other antigens.