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CA 19-9

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Also known as: Carbohydrate Antigen 19-9; Cancer Antigen-GI; CA-GI
Formal name: Cancer Antigen 19-9

At a Glance

Why Get Tested?

To help differentiate between cancer of the pancreas and other conditions; to monitor response to pancreatic cancer treatment and to watch for recurrence

When to Get Tested?

When your doctor suspects that you have pancreatic cancer and during or following pancreatic cancer treatment

Sample Required?

A blood sample drawn from a vein in your arm

Test Preparation Needed?


The Test Sample

What is being tested?

Cancer antigen 19-9 (CA 19-9) is a protein that exists on the surface of certain cancer cells. CA 19-9 does not cause cancer; rather, it is shed by the tumor cells, making it useful as a tumor marker to follow the course of the cancer.

CA 19-9 is elevated in 70% to 95% of people with advanced pancreatic cancer, but it may also be elevated in other cancers, conditions, and diseases such as colorectal cancer, lung cancer, gallbladder cancer, bile duct obstruction (e.g., gallstones), pancreatitis, cystic fibrosis, and liver disease. Small amounts of CA 19-9 are present in the blood of healthy people.

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein in the arm.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

No test preparation is needed.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

(Revised 2012 October 18). American Cancer Society. Tumor Markers [On-line information]. PDF available for download at through Accessed October 2012.

Thaker, N. et. al. (Updated 2012 May 23). CA 19-9. Medscape Reference [On-line information]. Available online at through Accessed October 2012.

(© 1995-2012). Carbohydrate Antigen 19-9 (CA 19-9), Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at through Accessed October 2012.

(© 2012). Diagnosis CA 19-9. Pancreatic Cancer Action Network [On-line information]. Available online at through Accessed October 2012.

Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 208-209.

Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pg 500.

Sources Used in Previous Reviews

Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].

Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.

ACS. All About Pancreatic Cancer, Pancreatic Cancer Detailed Guide. American Cancer Society.

ASCO (1996 May 17, adopted, revision every 3 years). CA 19-9 as a Marker for Colon Cancer. American Society for Clinical Oncologists, Clinical Practice Guidelines for the Use of Tumor Markers in Breast and Colorectal Cancer [On-line guidelines]. Available online at through

NCI (2002, February 8, posted). What you Need to Know about Cancer of the Pancreas. National Cancer Institute, [On-line information]. Available online through

Reid, C. (1996 October). Probing the Pancreas. U.S. Food and Drug Administration [On-line article]. Available online at through

Mayer, R. (1999 - 2002 copyright). Pancreatic Cancer. The National Pancreas Foundation [On-line article]. Available online at through

Check, W. (1998 July) Reaching agreement on tumor markers. CAP Today, In the News [On-line journal]. Available online at through

NCI (1998 April 27). Tumor markers. National Cancer Institute, Cancer Facts [On-line information]. Available online at through

ACS (2000 July 19). Tumor Markers. American Cancer Society, Prevention and Early Detection [On-line information]. Available online through

Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 216-217.

Clarke, W. and Dufour, D. R., Editors (© 2006). Contemporary Practice in Clinical Chemistry: AACC Press, Washington, DC. Pg 246.

(Revised 2008 December 08). Tumor Markers. American Cancer Society [On-line information]. Available online at through Accessed August 2009.

(Updated 2009 May) Tumor Markers. ARUP Consult [On-line information]. Available online at through Accessed August 2009.

Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Burtis CA, Ashwood ER and Bruns DE, eds. 4th ed. St. Louis, Missouri: Elsevier Saunders; 2006 Pg 773.