1.What is carcinoembryonic antigen? (1) Carcinoembryonic antigen (CEA) is a polysaccharide-rich protein complex that exists on the surface of malignant tumor cells and is a soluble acidic glycoprotein. (2) Carcinoembryonic antigen acts as an antigen and can elicit an immune response in patients. (3) Early fetal gastrointestinal tract and some tissues have the ability to synthesize CEA, but the content gradually decreases after 6 months of gestation, and the content is extremely low after birth. 2.What is serum carcinoembryonic antigen test? Serum CEA test is a quantitative test to determine the amount of CEA in serum, and the test result is expressed as ng/ml of CEA per ml of serum. 3.What is the biological reference interval of serum carcinoembryonic antigen test? Serum CEA <5ng/ml (RIA, CLIA, ELISA) Note: 1ng/ml=1ug/L 4.What is the clinical significance of abnormal serum carcinoembryonic antigen test? (1) Elevated CEA is mainly seen in patients with pancreatic cancer, colon cancer, rectal cancer, breast cancer, stomach cancer, lung cancer, etc. (2) Dynamic observation Generally, the concentration of CEA decreases when the disease improves, but may increase when the disease worsens. (3) Mildly elevated CEA is also common in patients with colitis, pancreatitis, liver disease, emphysema and bronchial asthma. (4) Serum CEA concentration is less than 2.5 ng/ml in 96%-97% of healthy non-smokers, while 20-40% of heavy smokers have CEA > 2.5 ng/ml and a few have > 5 ng/ml. (5) Serum CEA may also be mildly to moderately elevated in intestinal obstruction, biliary obstruction, pancreatitis, ulcerative colitis, cirrhosis, pneumonia, bronchitis, tuberculosis, emphysema and autoimmune diseases. There can be mild to moderate elevation, but it is usually intermittent and tends to disappear when the condition improves. (6) Patients who have frequent contact with animals or animal serum products may have false elevation in the test results. 5.Is there any early diagnostic value of serum carcinoembryonic antigen test? (1) CEA is a broad-spectrum tumor marker, which can be expressed in a variety of tumors with low organ specificity, and is mainly used clinically to assist in the diagnosis of malignant tumors, determine prognosis, monitor the efficacy and tumor recurrence. (2) CEA is not a specific marker for malignant tumors and has only auxiliary value in diagnosis. (3) The significance of carcinoembryonic antigen lies in its ability to reflect the existence of many kinds of tumors, but its specificity is not strong, its sensitivity is not high, and its role in early diagnosis of tumors is not obvious. (4) Combined testing with other tumor marker items can improve the positive rate of tumor diagnosis.