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  • Also Known As:
  • CA19-9
  • CA 19-9
  • CA 19-9 Assay
  • CA 19-9 Radioimmunoassay
  • Cancer-Associated Antigen 19-9
  • Carbohydrate Antigen 19-9
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Test Quick Guide

Cancer antigen 19-9 (CA 19-9) is a protein found in the blood. When found at elevated levels, CA 19-9 may indicate the presence of certain types of cancers or noncancerous conditions.

CA 19-9 testing is used alongside other types of testing, such as imaging, to help diagnose disease, monitor a patient’s response to treatment, and assist in detecting the return of a disease after treatment.

About the Test

Purpose of the test

The purpose of a CA 19-9 test is to measure the amount of CA 19-9 in the blood. CA 19-9 is a type of tumor marker. Tumor markers are substances found in tissue, blood, or other body fluids that may be a sign of cancer or certain noncancerous conditions. Testing may be performed for a number of reasons, including:

  • Diagnosing cancer and other medical conditions: CA 19-9 can be elevated as a result of pancreatic cancer and other cancers of the digestive system. It can also be increased by non-cancerous conditions such as scarring of the liver. Because it may be affected by multiple conditions, CA 19-9 testing is not used as the only test to make a diagnosis. Instead, CA 19-9 measurements are usually combined with the results of other tests, such as imaging and biopsy, to diagnose cancer or other diseases.
  • Evaluating cancer treatment: For people who have already been diagnosed with cancer, periodic monitoring of CA 19-9 can help doctors evaluate how the cancer is responding to treatment. In patients with pancreatic cancer, for example, a CA 19-9 level will generally be taken after diagnosis. This is referred to as a baseline measurement and can be compared to future levels taken during or after treatment.
  • Estimating cancer prognosis: The level of elevation of CA 19-9, both at initial diagnosis and after treatment, is one of several factors that may help doctors estimate a patient’s prognosis. Prognosis is the likely outcome of a disease, and it can also be affected by things like the stage or extent of a disease, any coexisting conditions, and a patient’s overall health.
  • Monitoring for cancer recurrence: Doctors may use CA 19-9 testing to evaluate pancreatic cancer patients who have received treatment with surgery to check for evidence of a recurrence. A recurrence is the return of a disease, usually after a period of time when it was not detectable.

CA 19-9 testing is not indicated for use as a method to screen for cancer. Screening refers to searching for evidence of a disease when there are no symptoms.

What does the test measure?

CA 19-9 testing measures the amount of cancer antigen 19-9 released into the bloodstream. This substance is produced by many cells in the body, including some types of healthy cells and certain cancer cells.

Finding a CA 19-9 Test

How to get tested

Procedures for collecting a blood sample used for CA 19-9 testing are performed in a doctor’s office, hospital, laboratory, or other medical setting after being ordered by a healthcare professional.

Can I take the test at home?

Tests to measure CA 19-9 in the blood are not currently available as an at-home test kit.

How much does the test cost?

The cost of CA 19-9 testing depends on a variety of factors, such as a patient’s health insurance coverage, where the test is performed, and any additional testing that is conducted at the same time. Total costs may include those associated with obtaining and analyzing the test sample as well as charges for an office visit.

CA 19-9 testing may be covered by health insurance. It could help to contact the health insurance provider or the hospital or laboratory conducting the test for more information about out-of-pocket costs, such as copays or deductibles.

For patients without health insurance, or for whom insurance doesn’t cover the cost of testing, a doctor or hospital administration can further discuss the out-of-pocket cost of CA 19-9 testing.

Taking a CA 19-9 Test

A CA 19-9 test is usually performed on a sample of blood. A health care professional will take a blood sample from a vein in your arm using a small needle.

Before the test

You generally don’t need to take any special preparations for a CA 19-9 blood test, but you can check with your doctor for any pretest instructions to follow.

During the test

During the test, a health professional draws blood, usually from a vein located on the inside of the elbow or the back of the hand. A blood draw generally involves the following steps:

  1. An elastic band is used as a tourniquet around the upper arm. This will make the veins beneath the band swell with blood.
  2. The site where the needle will be inserted is cleaned with an antiseptic wipe.
  3. A small needle is inserted into the vein.
  4. Blood collects into a vial or tube attached to the needle.
  5. The elastic band is removed.
  6. The needle is removed, and the site is covered with a bandage.

You may feel slight pain or a sting when the needle is inserted. Some people may experience dizziness, sweating, or nausea during the test. The test usually takes 5-10 minutes.

After the test

There is very little risk to having a blood test. You may have swelling, tenderness, inflammation, bruising, or persistent bleeding at the injection site. However, most symptoms go away quickly. Rare adverse effects may include infection. Contact your doctor if you have signs of an infection or any long-lasting effects.

Talk with your doctor if you have any concerns regarding the potential side effects associated with testing, including whether there are any restrictions to work or other activities.

CA 19-9 Test Results

Receiving test results

Patients can expect to receive the results of their CA 19-9 test within a few business days after the laboratory receives the blood sample. Your doctor may contact you directly, or a follow-up visit may be scheduled to discuss the findings of the test. Sometimes test reports are made available via an online health portal, or a physical copy can be sent by mail.

In some cases, doctors may wait to share the results of CA 19-9 testing until additional testing has been completed.

Interpreting test results

CA 19-9 levels are measured in units per millimeter (U/mL). The test report may also include an interpretation of the measurement, such as whether it is normal or abnormal.

Normal levels typically range between 0-37 U/mL. CA 19-9 levels can be elevated in healthy people without any underlying illness. High CA 19-9 levels can also be related to various conditions including:

  • Cancers of the pancreas, colon and rectum, liver, gallbladder, bile duct, stomach, ampulla of Vater, ovary, and bladder
  • Cholangitis, which is an infection of the bile ducts
  • Pancreatitis, which is inflammation of the pancreas
  • Cirrhosis of the liver
  • Bile duct obstruction, such as from gallstones

Because elevated levels are not always a sign of a health problem, research is still determining how to interpret CA 19-9 testing for diagnosis, prognosis, and treatment of various conditions. As such, CA 19-9 testing is most frequently used alongside other types of testing.

It is important for patients to discuss the meaning of their CA 19-9 test with their doctor, who is in the best position to explain its significance in their individual situation.

The way that CA 19-9 testing is interpreted can depend on the context in which the testing is used:

  • Diagnosis: As a diagnostic test, an elevated CA 19-9 level may suggest the presence of cancer or other conditions; however, it should not be used as the only test to make a diagnosis. Measurements are usually interpreted with the results of other tests, such as imaging and biopsy.
  • Monitoring: CA 19-9 levels may be monitored periodically during or after cancer treatment. This can help doctors evaluate how a patient’s cancer is responding to treatment. A fall in CA 19-9 levels could help confirm the effectiveness of a particular treatment. Conversely, a rise in CA 19-9 levels could indicate a need to change the treatment regimen.
  • Predicting prognosis: CA 19-9 test results may be used to help estimate cancer prognosis, but it is not used alone for this purpose. For some types of cancer, patients with high levels of CA 19-9 at diagnosis or shortly following treatment may have a worse prognosis than those with lower CA 19-9 levels.
  • Detecting recurrence: CA 19-9 levels that start low and later increase can point to cancer that has come back after a patient has completed treatment. Rising CA 19-9 levels usually precede other evidence of recurrent disease seen on imaging tests like a CAT scan or MRI. However, a rising CA 19-9 does not always indicate a recurrence, so confirmation of disease progression should be pursued with imaging studies and/or biopsy.

Because CA 19-9 levels are interpreted based on the specific situation, a doctor is best able to explain the significance of a CA 19-9 test result.

Are test results accurate?

Laboratories can use different methods to measure CA 19-9. For this reason, patients undergoing serial monitoring of CA 19-9 levels should verify that the same method is being used for each test. The test report typically lists the method used to assess CA 19-9 levels.

Do I need follow-up tests?

CA 19-9 testing is generally used alongside other types of testing. Other tests that may be done with CA 19-9 testing or as follow-up include imaging tests like a CAT scan, PET scan, or MRI as well as other laboratory tests and, when necessary, a biopsy.

Questions for your doctor about test results

When reviewing your CA 19-9 test with your doctor, some of the following questions may help you best understand the test’s significance in your case:

  • How do the results of my CA 19-9 test relate to my diagnosis and care?
  • Should I have any other tests in addition to the CA 19-9 test?
  • How frequently will I have CA 19-9 testing after I complete treatment?
  • What happens if my CA 19-9 levels increase after treatment?
  • Will all of my CA 19-9 tests use the same laboratory method?

View Sources


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