CA 19-9 Blood Test (Pancreatic Cancer)
Reviewed
Also called: cancer antigen 19-9, carbohydrate antigen 19-9, CA 19-9 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.
Specimen: Blood
Why this test may be ordered
- To monitor cancer treatment and see if it is working.
- To help make a prognosis by determining cancer stage and likelihood of treatment response.
- To check whether cancer has returned after treatment.
- If you have symptoms such as jaundice, weight loss, abdominal pain, or a swollen gallbladder or liver that may be linked to cancer.
Preparation and collection
Usually, you don't need any special preparations for a CA 19-9 blood test. But ask your provider to be sure. If you take certain vitamins, you may need to stop them before the test.
A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.
There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.
Understanding results
If you're being treated for cancer, you may be tested several times during your treatment. Your provider will look at all your test results to see how your CA 19-9 levels have changed.
- CA 19-9 levels are increasing: Your levels of CA 19-9 are increasing. This may mean your tumor is growing, and/or your treatment is not working. Limitation: More tests are usually needed to find out for sure. Next step: Your provider will look at all your test results to see how your CA 19-9 levels have changed.
- CA 19-9 levels are decreasing: Your levels of CA 19-9 are decreasing. This may mean your tumor is shrinking and your treatment is working. Limitation: The test method can affect your results. Next step: 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.
- CA 19-9 levels have stayed the same: Your levels of CA 19-9 have stayed the same. This may mean your disease is stable and hasn't gotten better or worse. Limitation: Labs use different methods to measure the amount of CA 19-9 in your blood sample. Next step: This allows your provider to compare your results over time.
- CA 19-9 levels decreased after treatment but later increased: Your CA 19-9 levels decreased after treatment but increased later. This may mean your cancer has come back or grown. Limitation: You'll need more tests to check whether cancer is really causing the higher level of CA 19-9. Next step: Talk with your provider about what your results may mean.
- High CA 19-9 in someone without cancer: If you don't have cancer but your test results show a high level of CA 19-9, you may not have a health problem that needs treatment. But high levels may be a sign of a condition, such as pancreatitis or gallstones. Limitation: Healthy people can have high CA 19-9 levels. Next step: If your provider thinks you may have one of these conditions, you will probably need other tests to find out for sure.
- High CA 19-9 levels can be caused by noncancerous conditions such as gallstones, pancreatitis, cirrhosis, or liver disease.
- Some people do not produce CA 19-9 even when they have a cancer that usually causes high levels, making the test unhelpful for them.
- Different labs may use different test methods, which can affect results. Consistency in lab testing is important for accurate monitoring.
- A CA 19-9 test cannot be used alone to screen for or diagnose cancer; it must be combined with other tests and clinical evaluation.
What to do next
Talk with your provider about what your results may mean. If you have any questions about how your tests are done, talk with your provider.
- What do my CA 19-9 results mean for my cancer treatment?
- How often should I have this test done?
- If my CA 19-9 level is high but I do not have cancer, what conditions might cause it?
- Do I need to have all future tests done at the same lab for comparability?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: CA 19-9 Blood Test (Pancreatic Cancer)