Other names: cancer antigen 19-9, carbohydrate antigen 19-9, CA 199 measurement, CA 19-9 radioimmunoassay (RIA)
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.
Why do I need a CA 19-9 test?
- 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.
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
Learn more about laboratory tests, reference ranges, and understanding results.
Is there anything else I need to know about a CA 19-9 test?
Labs use different methods to measure the amount of CA 19-9 in your blood sample. The test method can affect your results. If you're having regular tests to monitor cancer, it's important to have your tests done the same way, and usually in the same lab. This allows your provider to compare your results over time. Your test report usually says what method was used to measure your CA 19-9 levels. If you have any questions about how your tests are done, talk with your provider.
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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.
During cancer treatment, your health care provider may test you on a regular basis 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.
If you don't have cancer but your test results show a high level of CA 19-9, you may not a health problem that needs treatment. Healthy people can have high CA 19-9 levels. But high levels may be a sign of a condition, such as:
- Pancreatitis, inflammation of the pancreas
- Bile duct disease, including a blockage or infection
- Liver disease
- Cystic fibrosis
Talk with your provider about what your results may mean. If your provider thinks you may have one of these conditions, you will probably need other tests to find out for sure.
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