CA 19-9 test: what it shows and how the result is read

CA 19-9 (carbohydrate antigen 19-9) is a protein whose amount in the blood is measured as a so-called tumour marker. It is produced by both healthy and damaged cells of the pancreas, bile ducts, stomach and bowel, so a raised CA 19-9 on its own is not proof of cancer. According to MedlinePlus, the test is most often ordered not as primary cancer screening but together with imaging tests and biopsy — to follow the course of treatment of already diagnosed cancer of the pancreas, bile ducts, colon, stomach, ovary or bladder. A rising value during treatment may indicate that the tumour is growing, a falling one a response to treatment, and a rise after treatment a possible relapse. CA 19-9 can also be raised without any oncological disease — in gallstone disease, inflammation or infection of the bile ducts, inflammation of the pancreas (pancreatitis), liver cirrhosis or cystic fibrosis. That is why the result is always assessed by a doctor together with other tests and symptoms.

• To follow the course of treatment of already diagnosed cancer of the pancreas, bile ducts, colon, stomach, ovary or bladder
• To assess whether the treatment is working — comparing the change in the value over time with earlier results
• After cancer treatment — to watch whether the value starts rising again (a possible sign of relapse)
• Together with imaging tests and biopsy, when a disease of the pancreas or bile ducts is suspected
• When there are symptoms or findings that raise a suspicion of a disease of the digestive tract or the pancreas

How to prepare

• According to MedlinePlus, a CA 19-9 blood test usually needs no special preparation, but it is worth checking with your doctor
• If you take certain vitamins, you may need to stop them before the test
• It is worth mentioning to your doctor any liver, gallbladder or pancreas conditions you have — they can affect the result even without cancer

What counts as a normal CA 19-9

There is no single international norm limit — MedlinePlus states that the reference interval depends on the method of the particular laboratory, so the exact norm has to be looked up on the report sheet next to the result, and the value itself should always be discussed with a doctor.

A raised CA 19-9

A raised CA 19-9 is not in itself a diagnosis of cancer. According to MedlinePlus, it can rise in cancer of the pancreas, bile ducts, colon, stomach, ovary or bladder, but also in gallstone disease, infection of the bile ducts, inflammation of the pancreas, liver cirrhosis or cystic fibrosis. Even with no disease at all, the value is sometimes raised.

• Cancer of the pancreas, bile ducts, colon, stomach, ovary or bladder
• Gallstone disease or an infection of the bile ducts (cholangitis)
• Inflammation of the pancreas (pancreatitis)
• Liver disease, including liver cirrhosis
• Cystic fibrosis
• A raised value in a healthy person with no diagnosed disease

What to discuss with a doctor

• The result is always assessed by a doctor together with imaging tests (ultrasound, CT or MRI) and clinical findings, not by the value on its own
• If the test is being done to follow treatment — the direction of change in the value over time matters more than one single value
• The state of the liver and biliary tract — whether there is gallstone disease, inflammation or cirrhosis that could explain the result without an oncological cause
• When to repeat the test so that the trend can be seen

Related pages: AFP, how to prepare for a blood test and how to read blood test results.