CA 19-9

CA 19-9 (Carbohydrate Antigen 19-9) is a tumor marker primarily used in the management of pancreatic cancer. It is a type of glycoprotein that is produced by certain types of cancer cells and can be measured in the blood.

Discovery and Structure

CA 19-9 was first identified in the early 1980s. It is a sialylated Lewis(a) antigen, which is a type of carbohydrate antigen. The structure of CA 19-9 includes a carbohydrate moiety that is recognized by specific monoclonal antibodies.

Clinical Use

CA 19-9 is most commonly used in the diagnosis and management of pancreatic cancer. Elevated levels of CA 19-9 can also be seen in other conditions such as cholangiocarcinoma, colorectal cancer, and hepatocellular carcinoma. However, it is not specific enough to be used as a sole diagnostic tool.

Diagnostic Role

CA 19-9 is often used in conjunction with other diagnostic tests such as imaging studies and biopsy to confirm the presence of pancreatic cancer. It is particularly useful in monitoring the response to treatment and in detecting recurrence after treatment.

Limitations

One of the limitations of CA 19-9 is that it can be elevated in benign conditions such as pancreatitis, cirrhosis, and cholecystitis. Additionally, about 5-10% of the population lacks the Lewis antigen and therefore cannot produce CA 19-9, making the test ineffective for these individuals.

Interpretation of Results

The normal reference range for CA 19-9 is typically less than 37 U/mL. Levels above this range may indicate the presence of malignancy, but further diagnostic workup is necessary to confirm the diagnosis.

Related Pages

• Pancreatic cancer
• Tumor marker
• Glycoprotein
• Cholangiocarcinoma
• Colorectal cancer
• Hepatocellular carcinoma
• Pancreatitis
• Cirrhosis
• Cholecystitis

See Also

• CEA (Carcinoembryonic Antigen)
• AFP (Alpha-fetoprotein)
• PSA (Prostate-Specific Antigen)