Cancer Antigen 19.9 or Carbohydrate Antigen 19.9 (CA 19.9) is a protein found in the blood. When detected in high quantities, it acts as a tumour marker. Higher than typical amounts of CA 19.9 in the bloodstream indicate the possibility of cancer in the pancreas, colon, stomach, and bile duct.

Who Needs to Undergo a CA 19.9 Blood Test?

A CA 19.9 blood test is not only a diagnostic test for pancreatic cancer but also an indicator of how well the treatment is working. Doctors usually prescribe this blood test for:

• Individuals diagnosed with tumours associated with high levels of serum cancer antigen 19.9 in their bloodstream
• People at a high risk of developing pancreatic and colon cancers
• Individuals with a family history of the condition
• People living with diabetes and hepatitis B

Is CA 19.9 a Reliable Biomarker For Pancreatic Cancer?

Biomarkers are biomolecules in your body that indicate the presence or absence of a biological condition. These biomarkers may be present in the tissues, body fluids or bloodstream. The serum cancer antigen 19.9 is the only validated and clinically useful biomarker in the detection of pancreatic cancer till now. It has a sensitivity of 79-81% for diagnosing pancreatic cancer. This tumour marker is instrumental in designing a prognosis and predicting the overall survival rate of an individual with pancreatic cancer.

Preparing For CA 19.9 Blood Test

Although there are no special requirements for the CA 19.9 blood test preparation, keep the following things in mind:

• Inform your doctor about any medications you are consuming.
• Intimate your doctor regarding any allergies you may have.
• If there has been an incident of an animal bite, inform your doctor about it. Antibodies would be present in your body because of the incident that may interfere with the test results.
• Avoid taking multivitamins or dietary supplements containing biotin (vitamin B7) at least 12 hours before the test to prevent false positive results.

Uses of a CA 19.9 Blood Test

The CA 19.9 blood test should not be considered exclusively as a screening test for pancreatic cancer, though it is essential in its diagnosis. This test finds more applications in the management of the condition. The uses of this test are enumerated below:

• Clubbed with imaging and biopsy tests, it helps detect pancreatic or digestive cancers.
• It helps in monitoring the progress of pancreatic cancer. Increased or decreased levels of the serum cancer antigen 19-9 in the bloodstream indicate the spread or shrinkage of the tumour.
• It gives a fair idea of how the current treatment plan is working.
• It assesses if a relapse has occurred post-treatment.
• It is a part of follow-up care and prognosis for pancreatic cancer.

What do the results mean?

If you’re being treated for cancer, you may be tested several times during your treatment. Your oncologist will look at all your test results to see how your CA 19.9 levels have changed. 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. More tests are usually needed to find out for sure.
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 stayed the same. This may mean your disease is stable and hasn’t gotten better or worse.
Your CA 19-9 levels decreased after treatment, but increased later. This may mean your cancer has come back or grown. You’ll need more tests to check whether cancer is really causing the higher level of CA 19.9.

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
• Gallstones
• Bile duct disease, including a blockage or infection
• Liver disease
• Cystic fibrosis