CEA is an oncofetal antigen, a glycoprotein that is usually produced only during fetal life and is not present in the healthy adult blood. It is associated with certain malignancies, particularly epithelial tumors. It is a very non-specific tumour marker. Normal values: Non-smokers: 0–3 ng/mL [μg/L] Smokers: 0-5 ng/mL [μg/L] Elevated levels in: 1) Adenocarcinoma of colon cancer (72%) (right side of colon>left side), 2) Pancreatic cancer (91%), 3) Lung cancer (76%), 4) Stomach cancer (61%), 5) Breast cancer, 6) Cancer of ovary, 7) Cholangiocarcinoma, 8) Gall bladder cancer. Other non-neoplastic conditions include: 1) Cigarette smokers, 2) Benign liver disease (acute 50% and chronic 90%), 3) Benign GI disease (peptic ulcer, pancreatitis, colitis,cholecystitis). Elevations >20 ng/mL are generally associated with malignancy and metastasis. Screening: The test is not sensitive or specific enough to be useful in cancer screening