Description
What is a CA 19-9 blood test?
A CA 19-9 test measures the amount of a protein called CA 19-9 (cancer antigen 19-9) in a sample of your blood. CA 19-9 is a type of tumor marker. Tumor markers are substances made by cancer cells or by normal cells in response to cancer in your body.
Healthy people can have small amounts of CA 19-9 in their blood. High levels of CA 19-9 are often a sign of pancreatic cancer. But high levels can also be a sign of other types of cancer or certain conditions that aren’t cancer. For example, gallstones and cirrhosis of the liver can cause high CA 19-9 levels.
Because high levels of CA 19-9 can mean different things, the test is not used by itself to screen for or diagnose cancer or other diseases. But it can help monitor your cancer and check how well your treatment is working.
Other names: cancer antigen 19-9, carbohydrate antigen 19-9, CA 199 measurement, CA 19-9 radioimmunoassay (RIA)
What is it used for?
CA 19-9 blood tests may be used to:
Monitor certain types of cancer and cancer treatment. CA 19-9 levels often go up as cancer grows and go down as tumors shrink.
- Help predict how cancer may behave over time.
- Check whether cancer has returned after treatment.
- Help diagnose certain cancers and other diseases when used with other tests.
Some people do not make CA 19-9 even when they have a cancer that usually produces high levels of CA 19-9. For these people, a CA 19-9 tumor marker test is not useful.
Why do I need a CA 19-9 test?
You may need a CA 19-9 blood test if you’ve been diagnosed with pancreatic cancer or another type of cancer that causes high CA 19-9. These include cancers of the:
- Bile duct
- Colon and rectum
- Stomach
- Ovaries
- Bladder
Your healthcare provider may test you regularly during cancer treatment to see if your treatment is working.
After your treatment is complete, you may need to have CA 19-9 tests to check whether the cancer has come back. High levels of CA 19-9 may be one of the first signs that cancer cells are growing again.
