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CA 19.9 Blood Test

Last updated Nov. 22, 2018

Approved by: Krish Tangella MD, MBA, FCAP

CA 19-9 Test is a test to detect and measure the amount of CA 19-9 (Cancer Antigen 19-9), a tumor marker, in blood.

What are the other Names for this Test? (Equivalent Terms)

  • CA-G1 Test
  • Cancer Antigen 19-9 Test
  • Carbohydrate Antigen 19-9 Test

What is CA 19.9 Blood Test? (Background Information)

  • CA 19-9 Test is a test to detect and measure the amount of CA 19-9 (cancer antigen 19-9), a tumor marker in blood
  • CA 19-9 is a protein secreted by the some pancreatic and gastrointestinal cancer cells. It can be detected in blood when these cancers are present
  • CA 19-9 Test helps diagnose and monitor the cancer. It is also used to evaluate the effectiveness of treatment. However, this test is not used for screening cancer, as the disease is mostly in its advanced cancerous stages by the time signs and symptoms appear and levels of CA 19-9 rise
  • The use of this test is limited to diagnosing and monitoring those cases of cancer (affecting the pancreas or gastrointestinal tract), which secrete high levels of CA 19-9 protein

What are the Clinical Indications for performing the CA 19.9 Blood Test?

  • Though CA 19-9 Test is not diagnostic of any particular type of cancer due to its low specificity (indication of cancer) and sensitivity (affectability), It is ordered along with other tests and investigations by the healthcare provider, in cases when pancreatic cancer is suspected. Some of the signs and symptoms of pancreatic cancer are:
    • Weakness and fatigue
    • Loss of weight
    • Loss of appetite
    • Nausea and vomiting
    • Pain in the abdomen
    • Yellowness of the skin and white of the eye
  • The test is generally ordered along with other tests and investigations before the treatment is started and then, ordered periodically to monitor the effect of treatment, or recurrence of cancer.This test is also ordered as part of the work-up, if the tumor is removed surgically or treatment for advanced pancreatic cancer has been started
  • CA 19-9 Test may also be ordered when the healthcare provider wishes to rule out cancer of the bile duct (hepatobiliary cancer) in cases where signs and symptoms present (such as abdominal pain, fever, itching, yellowness of skin and white of the eye, dark urine, and pale-colored stool), points to the obstruction of the bile duct.

How is the Specimen Collected for CA 19.9 Blood Test?

Sample required: Blood

Process: Insertion of needle into a vein (arm).

Preparation required:None

What is the Significance of the CA 19.9 Blood Test Result?

  • Normal reference range of CA 19-9 for both males and females is 0-37 U/mL (‘U’is not defined). Increasing levels of CA 19-9 signify progression of the cancer.About 70-95% of individuals with advanced pancreatic cancer will show elevated levels of CA 19-9
  • Increased levels of CA 19-9 correlate with the spread of pancreatic cancer despite treatment, or the return of the cancer (after being successfully treated)
  • Elevated levels of CA 19-9 may also be found in some other cases, such as cancer of the lung, gallbladder, and colorectal cancer, liver disease, cystic fibrosis, gallstones, and pancreatitis (inflammation of pancreas). Clinical signs and symptoms and other testing will help establish a definitive diagnosis in all cases
  • Based on the levels of CA 19-9, it helps one distinguish pancreatic cancer from some other conditions, such as inflammation of the pancreas. The levels with pancreatic cancer are generally extremely high, without treatment. However, with pancreatitis, the levels of CA 19-9 drop or increase based on a decrease or increase in the inflammation of pancreas
  • If the levels start decreasing after initiation of treatment, it usually signifies effective therapy and response to treatment. Constant levels are associated with stable disease.
  • Level of CA 19-9 rises in about 65% cases of bile duct cancer. Level of CA 19-9 can also be high during bile duct obstruction. But, if no cancer is present, the levels will fall within two weeks (approximately) after the obstruction is cleared

The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.

Additional and Relevant Useful Information:

  • CA 19-9 can be found in low levels in normal individuals
  • Due to its effect on pancreatic cells, CA 19-9 Test results may be distorted in individuals receiving radiation treatment and so this test is not performed, while the individual is receiving radiotherapy

Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.

References and Information Sources used for the Article:

Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Sept. 4, 2013
Last updated: Nov. 22, 2018