Carcinoembryonic Antigen (CEA) – 002139

CEA is a monomeric glycoprotein (molecular weight approximately 180,000 daltons) with a variable carbohydrate component of approximately 45% to 60%.^1,2 CEA, like AFP, belongs to the group of carcinofetal antigens produced during the embryonic and fetal period. CEA is mainly found in the fetal gastrointestinal tract and in fetal serum. It also occurs in slight quantities in intestinal, pancreatic, and hepatic tissues of healthy adults. The formation of CEA is repressed after birth and, accordingly, serum CEA values are hardly measurable in healthy adults.

High CEA concentrations are frequently found in cases of colorectal adenocarcinoma.^3,4 Slight to moderate CEA elevations (rarely >10 ng/mL) occur in 20% to 50% of benign diseases of the intestine, pancreas, liver, and lungs (eg, liver cirrhosis, chronic hepatitis, pancreatitis, ulcerative colitis, Crohn’s disease, emphysema).^3,5 Smokers also have elevated CEA values. The reactive epitopes of CEA have been characterized, and the available monoclonal antibodies classified, into six epitope groups.^6-8 The antibodies used in the Elecsys CEA assay react with epitopes two and five. The antibodies react with CEA and (as with almost all CEA methods) with the meconium antigen (NCA2).⁸ Cross-reactivity with NCA1 is 0.7%.