The CA 19-9 test is a blood test that measures the level of carbohydrate antigen 19-9 (CA 19-9), a protein that can be produced by certain cancer cells as well as some normal cells.

What it is used for

CA 19-9 is not a screening test for cancer in healthy people. Instead, it is primarily used to:

• Monitor treatment for certain cancers, especially pancreatic cancer.

• Assess response to therapy (falling levels may suggest treatment is working).

• Detect recurrence after cancer treatment.

• Sometimes help evaluate a person with symptoms or imaging findings suggestive of certain cancers.

Cancers associated with elevated CA 19-9

High CA 19-9 levels may be seen in:

• pancreatic cancer (most commonly)

• bile duct cancer

• Gallbladder cancer

• Stomach (gastric) cancer

• Colorectal cancer

• Less commonly, other gastrointestinal cancers

Non-cancer conditions that can raise CA 19-9

CA 19-9 can also be elevated in several non-cancerous conditions, including:

• Gallstones

• Blocked bile ducts (biliary obstruction)

• Pancreatitis

• Liver disease (such as cirrhosis or hepatitis)

• Cystic fibrosis

Because of this, an elevated CA 19-9 does not necessarily mean a person has cancer.