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ASCA

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Also known as: Anti-Saccharomyces cerevisiae mannan antibodies
Formal name: Saccharomyces cerevisiae Antibodies, IgG or IgA

The Test Sample

What is being tested?

Anti-Saccharomyces cerevisiae antibodies (ASCA) are immune proteins that are frequently present in people who have inflammatory bowel disease (IBD). This test detects ASCA in the blood.

S. cerevisiae are common yeast found in various foods. The correlation between the presence of antibodies to S. cerevisiae and their involvement in the inflammatory bowel disease process is not understood at this time.

IBD is a group of chronic disorders, thought to be an autoimmune process, characterized by swollen and damaged tissues in the lining of the intestinal tract. The symptoms and severity of IBD vary from person to person and may fluctuate over time. Many of those affected experience flare-ups followed by periods of lessened symptoms or even remission.

Testing for ASCA can be useful in helping to distinguish between the two most common types of IBD, Crohn disease (CD) and ulcerative colitis (UC). CD can affect any part of the intestinal tract, from mouth to anus, but is primarily found in the small intestine and/or in the colon, while UC occurs in the colon.

The diagnosis of CD or UC is usually made on the basis of endoscopic testing and the examination of biopsy samples from the intestines. Because both CD and UC can be found in the colon, it can sometimes be difficult to distinguish between the two. When this occurs, ASCA testing may be helpful as ASCA is much more frequently found in people with CD than in those with UC.

There are two classes of Saccharomyces cerevisiae antibodies produced by the body, ASCA IgG and ASCA IgA. Testing usually includes both classes.

Sometimes several antibodies, including ASCA, perinuclear anti-neutrophil cytoplasmic antibody (pANCA), anti-CBir1 (anti-flagellin antibody), and anti-Omp C (anti-outer membrane protein antibody), may be ordered together as a panel and the overall findings evaluated to either help distinguish between CD and UC or to try to help determine a prognosis for a person's CD. The presence of multiple antibodies may indicate the likelihood of a more aggressive disease, but negative results do not rule out aggressive disease.

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.