Also known as:Anti-Saccharomyces cerevisiae mannan antibodies
Formal name:Saccharomyces cerevisiae Antibodies, IgG or IgA
Related tests:ANCA/MPO/PR3 Antibodies, Anti-CBir1, Anti-Omp C, Anti-I-2, Calprotectin, Lactoferrin, Fecal Occult Blood Test, Stool Culture, Clostridium difficile and C. difficile Toxin Testing, O&P
Why Get Tested?
To help distinguish between Crohn disease (CD) and ulcerative colitis (UC), the two most common types of inflammatory bowel disease (IBD); as an adjunct to other IBD testing
When to Get Tested?
When you have symptoms such as persistent or intermittent diarrhea and abdominal pain that your healthcare practitioner suspects may be due to an IBD; when your healthcare practitioner wants to distinguish between CD and UC
A blood sample drawn from a vein in your arm
Test Preparation Needed?
How is it used?
The test for anti-Saccharomyces cerevisiae antibodies (ASCA) is used to help distinguish between Crohn disease (CD) and ulcerative colitis (UC), the two most common types of inflammatory bowel disease (IBD). Testing usually includes detecting two different classes of ASCA in the blood, IgG and IgA.
ASCA are immune proteins that are frequently present in people who have IBD. The association between the presence of ASCA and their involvement in the disease process, however, is not understood at this time.
IBDs are primarily diagnosed through non-laboratory evaluations, such as a biopsy of the intestine. In some cases, however, it can be difficult to distinguish between CD and UC. An ASCA test is often ordered along with a test for perinuclear anti-neutrophil cytoplasmic antibody (pANCA) to help determine which type of IBD a person has. The presence of ASCA is more common in CD, while pANCA is more common in UC. Anti-CBir1 (anti-flagellin antibody) and anti-Omp C (anti-outer membrane protein antibody) are indicative of CD and may also be used in combination with ASCA testing.
Since the symptoms associated with IBD may be seen with a number of conditions, other tests are frequently performed prior to or along with ASCA testing to rule out other causes for the symptoms. For more on this, see the article on Inflammatory Bowel Disease.
When is it ordered?
ASCA testing is primarily ordered when a person has signs and symptoms that suggest IBD and a healthcare practitioner is attempting to distinguish between CD and UC. It may be ordered along with pANCA and other antibody testing.
Signs and symptoms of an IBD may include:
- Abdominal pain and cramps
- Rectal bleeding
- In some people, joint, skin, bone and organ-related symptoms
- Children may also have delayed development and growth retardation.
What does the test result mean?
A positive ASCA result is not diagnostic of CD, UC, or of an IBD, but it does make it more likely that a person with symptoms has an IBD.
Results of ASCA testing are often interpreted in conjunction with the results of pANCA testing:
- If ASCA is positive and pANCA is negative, then it is likely that the person has CD.
- If ASCA is negative and pANCA is positive, then it is likely that the person has UC.
A negative result for ASCA and pANCA does necessarily rule out IBD. A person who is negative may still have CD, UC, or another IBD.
The presence of multiple antibodies (ASCA, anti-CBir1, anti-Omp C) may indicate the likelihood of a more aggressive disease, but negative results do not rule out aggressive disease.
Is there anything else I should know?
There are many other antibody biomarkers that are associated with IBD.
The amount of ASCA and/or pANCA present does not correlate with the severity of a person's symptoms or condition and it cannot be used to monitor response to treatment.
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.
- Is it necessary to perform ASCA testing more than once?
Testing is usually only performed once, to help distinguish between CD and UC. It is typical to order tests for the two classes of antibody, ASCA IgG and ASCA IgA, at the same time. However, if only one of the types was initially ordered, then the other type (or more likely both) may be ordered at a later date.
- Should everyone with abdominal pain and diarrhea have this test performed?
No, it is not necessary in most cases as these symptoms are common and are most frequently due to something other than IBD. Most people will never need to have ASCA testing performed.
- Will ASCA go away once they have developed?
The level of antibody may vary over time, but once a person's body has produced ASCA, it will continue to be present.
- Can ASCA testing be performed in my doctor's office?
In general, no. It is not offered by every hospital laboratory. It may be necessary to send your blood sample to a reference laboratory for testing.
© 2017 American Association for Clinical Chemistry, republished from Lab Tests Online.*
Descriptions of clinical laboratory tests were originally prepared for use on Lab Tests Online, an award-winning patient education website on clinical laboratory testing. Lab Tests Online is produced by the American Association for Clinical Chemistry (AACC), a global scientific and medical professional organization dedicated to clinical laboratory science and its application to healthcare. The Lab Tests Online website is developed in collaboration with other laboratory professional societies and is funded in part through corporate sponsorships.