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Carbohydrate antigen 19-9 (CA19-9)

Carbohydrate antigen (CA19-9) is a protein that is found in very small amounts on the surface of certain cancer cells. It may be found in the blood when it is shed by tumour cells. It is also found in trace amounts in the pancreas, liver, gall bladder and lungs of healthy adults.

Why a CA19-9 test is done

A CA19-9 test may be done to check:

  • a person’s response to treatment for pancreatic cancer, especially advanced pancreatic cancer
    • This is the main use of CA19-9 tests.
  • if pancreatic cancer is still growing or has come back (recurred) after treatment

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How a CA19-9 test is done

A CA19-9 test is usually done in a private laboratory or hospital laboratory. No special preparation is usually needed.

  • CA19-9 is usually measured by a blood test.
  • The sample is sent to a laboratory to be analyzed by special machines.

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What the results mean

An increased CA 19-9 value can occur in non-cancerous and cancerous conditions.

  • non-cancerous conditions
    • liver diseases (such as cirrhosis or hepatitis)
    • inflammation of the gallbladder (cholecystitis) or gallstones
    • inflammation of the pancreas (pancreatitis)
    • cystic fibrosis
    • some disorders of the lung, kidney or gastrointestinal tract
  • cancerous conditions
    • pancreatic cancer
      • Higher levels of CA19-9 tend to be associated with more advanced pancreatic cancer.
      • CA19-9 is not usually increased in people with very early disease.
    • colorectal cancer
    • stomach cancer
    • liver cancer
    • bile duct cancer
    • lung cancer
    • breast cancer
    • uterine cancer
    • ovarian cancer

In cancerous conditions:

  • A decrease in, or return to normal values of, CA19-9 may mean that the cancer has responded well to treatment.
  • Anincrease may mean that the cancer is not responding well to treatment, is still growing or is coming back (recurring).
    • A slight increase may not be significant. The doctor looks at trends in the increase over time.

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What happens if a change or abnormality is found

The doctor will decide if more tests, procedures, follow-up care or additional treatment is needed.

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