CA 19-9 Blood Test

The CA 19-9 blood test checks the levels of carbohydrate antigen 19-9 (CA 19-9) in your blood. This antigen is a tumor marker, a substance that cancer produces. High CA 19-9 levels may be a sign of cancer. But many noncancerous issues can cause high levels. The antigen is also known as cancer antigen 19-9 or sialylated Lewis a antigen.

Healthcare providers may do a CA 19-9 test if you:

• Have cancer: Providers may do this test if you have pancreatic cancer or bile duct cancer. They’ll use CA 19-9 test results to plan treatment and see if treatment is working.
• Have certain signs or symptoms: Pancreatic cancer and bile duct cancer cause symptoms like belly pain or losing weight without trying. You may have a CA 19-9 test if an MRI or CT scan detects a mass in your belly.
• Have certain conditions: If you have chronic pancreatitis, intraductal papillary mucinous neoplasm (IPMN) or mucinous cystic lesions of the pancreas, you may have increased cancer risk. Another risk factor is diabetes that starts when you’re 50 and older.
• Have recurrent cancer: Your provider may do regular follow-up tests to check for signs that cancer has come back.

It’s important to remember that test results that show high CA 19-9 levels don’t mean you have cancer. Healthcare providers typically do biopsies to diagnose cancer.

What happens during a CA 19-9 blood test?

This test is just like the blood test you may have as part of your annual health checkup. You don’t need to do anything to get ready for it. Here’s what happens:

1. You’ll sit in a chair and place your arm on an armrest.
2. Your phlebotomist, who has special training in drawing blood, will wipe the inside of your elbow with an antiseptic liquid. They’ll put an elastic band just above your elbow.
3. They’ll insert a needle into your arm. You may feel a pinch. They may ask you to make a fist. Doing that helps blood flow. Typically, this test requires a small amount of blood.
4. After your phlebotomist obtains a blood sample, they’ll seal the tube. Then, they’ll release the elastic band on your arm and remove the needle.

What to expect after the test

Most people have a CA 19-9 blood test along with other tests. Your healthcare provider will check your test results and arrange a time to discuss them with you. Ask your provider when you can expect to learn your test results and next steps.

What do CA 19-9 test results mean?

This test measures CA 19-9 antigen in your blood. Because this is an antigen that is present in most people, there’s a normal range for the lab result. Levels higher than that range may be a sign of certain cancers, including pancreatic cancer. But they also may be a sign of noncancerous conditions.

Why would I have this test?

Healthcare providers may do this test after a diagnosis or suspected diagnosis of cancer in your:

• Pancreas
• Bile duct
• Stomach
• Colon and rectum
• Liver
• Ovaries
• Bladder
• Esophagus
• Lungs
• Thyroid

But other noncancerous conditions can cause high CA 19-9 levels, like:

• Bile duct issues, such as infections, inflammation or a blocked bile duct
• Gallstones
• Chronic hepatitis
• Chronic kidney failure
• Liver cirrhosis
• Autoimmune pancreatitis
• Lung disease
• Ovarian cystic tumors
• Rheumatic diseases
• Thyroid diseases

Does the test always detect pancreatic cancer?

Research shows the test accurately detects cancer in 8 out of 10 people who have symptoms of pancreatic cancer. But some people with pancreatic cancer have low levels of CA 19-9 because they don’t have the antigen that makes CA 19-9.

That can happen if they have a genetic change that affects the Lewis gene, which makes CA 19-9. Experts estimate that 5 to 10 out of 100 people in the world have no CA 19-9 or low levels of the tumor marker.

Is the CA 19-9 blood test a cancer screening test?

No, it’s not. Screening tests are routine tests, like a mammogram or PSA test, that you may have as part of your annual physical checkup. The tests check for signs of cancer that develop before you have symptoms.