CA 19-9 Blood Test

The CA 19-9 blood test is a diagnostic tool used to measure the level of a protein called carbohydrate antigen 19-9 (CA 19-9) in the blood.

Purpose

The primary purpose of the CA 19-9 blood test is to monitor and diagnose pancreatic cancer, as well as other types of cancer such as bile duct, gallbladder, and stomach cancer. It can also be used to assess the effectiveness of treatment for these conditions.

What is CA 19-9?

CA 19-9 is a type of antigen, a substance that triggers an immune response, produced by cancer cells in some types of tumors. In healthy individuals, low levels of CA 19-9 are present in the blood, but elevated levels can indicate the presence of cancer.

How is the test performed?

The CA 19-9 blood test involves a simple blood draw from a vein in the arm. The blood sample is then sent to a laboratory for analysis, where the level of CA 19-9 is measured using an immunoassay technique.

Interpretation of results

The results of the CA 19-9 blood test are typically reported as units per milliliter (U/mL). The normal range for CA 19-9 varies depending on the laboratory, but generally, a level below 37 U/mL is considered normal. Elevated levels may indicate:

• Pancreatic cancer: Levels above 1000 U/mL are often associated with advanced pancreatic cancer.
• Other types of cancer: Elevated CA 19-9 levels can also be seen in bile duct, gallbladder, and stomach cancer.
• Non-cancerous conditions: Certain non-cancerous conditions, such as pancreatitis, liver disease, and inflammatory bowel disease, can also cause elevated CA 19-9 levels.

Limitations of the test

The CA 19-9 blood test has several limitations:

• Lack of specificity: Elevated CA 19-9 levels are not exclusive to cancer and can be seen in non-cancerous conditions.
• Lack of sensitivity: Not all pancreatic cancers produce CA 19-9, so a normal result does not rule out the presence of cancer.
• False positives: Elevated CA 19-9 levels can occur in individuals with non-cancerous conditions, leading to false positive results.

Clinical use

The CA 19-9 blood test is typically used in conjunction with other diagnostic tools, such as imaging studies and biopsy, to:

• Monitor disease progression and response to treatment in patients with known pancreatic cancer.
• Aid in the diagnosis of pancreatic cancer and other types of cancer.
• Assess the risk of recurrence in patients who have undergone treatment for pancreatic cancer.