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CA 19-9

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Also known as: Carbohydrate Antigen 19-9; Cancer Antigen-GI; CA-GI
Formal name: Cancer Antigen 19-9

The Test Sample

What is being tested?

Cancer antigen 19-9 (CA 19-9) is a protein that exists on the surface of certain cancer cells. CA 19-9 does not cause cancer; rather, it is shed by the tumor cells, making it useful as a tumor marker to follow the course of the cancer.

CA 19-9 is elevated in 70% to 95% of people with advanced pancreatic cancer, but it may also be elevated in other cancers, conditions, and diseases such as colorectal cancer, lung cancer, gallbladder cancer, bile duct obstruction (e.g., gallstones), pancreatitis, cystic fibrosis, and liver disease. Small amounts of CA 19-9 are present in the blood of healthy people.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.