What is a CA 19-9 blood test?
This test measures the amount of a protein called CA 19-9 (cancer antigen 19-9) in the 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 the 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 sometimes, high levels can indicate other types of cancer or certain noncancerous disorders, including cirrhosis and gallstones.
Because high levels of CA 19-9 can mean different things, the test is not used by itself to screen for or diagnose cancer. It can help monitor the progress of your cancer and the effectiveness of cancer treatment.
Other names: cancer antigen 19-9, carbohydrate antigen 19-9
What is it used for?
A CA 19-9 blood test may be used to:
- Monitor pancreatic cancer and cancer treatment. CA 19-9 levels often go up as cancer spreads, and go down as tumors shrink.
- See if cancer has returned after treatment.
The test is sometimes used with other tests to help confirm or rule out cancer.
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 other type of cancer related to high levels of CA 19-9. These cancers include bile duct cancer, colon cancer, and stomach cancer.
Your health care provider may test you on a regular basis to see if your cancer treatment is working. You may also be tested after your treatment is complete to see if the cancer has come back.
What happens during a CA 19-9 blood 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.
Will I need to do anything to prepare for the test?
You don’t need any special preparations for a CA 19-9 blood test.
Are there any risks to the test?
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.
What do the results mean?
If you are being treated for pancreatic cancer or other type of cancer, you may be tested several times throughout your treatment. After repeated tests, your results may show:
- Your levels of CA 19-9 are increasing. This may mean your tumor is growing, and/or your treatment is not working.
- Your levels of CA 19-9 are decreasing. This may mean your tumor is shrinking and your treatment is working.
- Your levels of CA 19-9 have not increased or decreased. This may mean your disease is stable.
- Your CA 19-9 levels decreased, but then later increased. This may mean your cancer has come back after you’ve been treated.
If you do not have cancer and your results show a higher than normal level of CA 19-9, it may be a sign of one of the following noncancerous disorders:
- Pancreatitis, a noncancerous swelling of the pancreas
- Bile duct blockage
- Liver disease
- Cystic fibrosis
If your health care provider suspects you have one of these disorders, he or she will probably order more tests to confirm or rule out a diagnosis.
Talk to your health care provider if you have questions about your results.
Is there anything else I need to know about a CA 19-9 test?
CA 19-9 testing methods and results can vary from lab to lab. If you are getting tested regularly to monitor treatment for cancer, you may want to talk to your health care provider about using the same lab for all your tests, so your results will be consistent.