What are the methods used for checking CEA (carcinoembryonic antigen)?

Immunoenzymatic test. A very commonly established way to check for the presence of certain proteins in the blood/serum uses a combination of monoclonal antibodies directed at one part of the cea (carcinoembryonic antigen). One of the antibodies is linked to an enzyme which causes a chemiluminiscent reaction easily detected, the intensity of which corresponds to the amount of cea detected.