Test Catalog

Test ID: SCERA    
Saccharomyces cerevisiae Antibody, IgA, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Measurement of IgA anti-Saccharomyces cerevisiae antibodies as a part of a profile to aid in distinguishing between ulcerative colitis and Crohn disease in patients for whom the specific diagnosis is unclear based on endoscopic, pathologic, and imaging evaluations


This test is not useful for determining the extent of disease in patients with inflammatory bowel disease or determining the response to disease-specific therapy including surgical resection of diseased intestine

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Inflammatory bowel disease (IBD) refers to 2 diseases - ulcerative colitis (UC) and Crohn disease (CD), both of which result from chronic inflammation in the gastrointestinal (GI) tract.(1) CD is characterized by chronic diarrhea, abdominal pain, and fatigue.(2) In comparison, UC frequently presents with bloody diarrhea that is of an urgent nature.(3) Inflammation in UC most frequently affects the rectum and proximal colon, and presents with continue mucosal involvement. In CD, inflammation can affect almost any area of the GI tract and is usually evidenced as patchy, transmural lesions.


Diagnosis of IBD is primarily based on clinical evaluation, endoscopy with biopsy, and imaging studies.(4) Because CD and UC are characterized by GI inflammation, fecal calprotectin can be used to differentiate IBD from noninflammatory conditions such as irritable bowel syndrome (IBS). Fecal calprotectin is useful in excluding IBD as a diagnosis and avoiding unnecessary endoscopic or imaging procedures.


CD and UC are associated with the presence of various antimicrobial and autoantibodies.(5) Patients with UC often have measurable antineutrophil cytoplasmic antibodies (ANCA), which react with as yet uncharacterized target antigens in human neutrophils; in contrast, patients with CD often have measurable IgA and/or IgG antibodies, which react with cell wall mannan of Saccharomyces cerevisiae. Despite these associations, current guidelines indicate that testing for these antibodies is not sufficiently sensitive for use in the diagnosis of IBD.(2,3) Rather, these antibodies should be limited to distinguishing between CD and UC in cases where the specific diagnosis is unclear from pathologic and imaging studies.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative: <20.0 RU/mL

Positive: > or =20.0 RU/mL

Reference values apply to all ages.

Interpretation Provides information to assist in interpretation of the test results

The presence of antineutrophil cytoplasmic antibodies (ANCA) in the absence of IgA and IgG anti-Saccharomyces cerevisiae antibodies (ASCA) is consistent with the diagnosis of ulcerative colitis (UC); the presence of IgA and IgG ASCA in the absence of ANCA is consistent with Crohn disease (CD).

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Results from this test should not be exclusively relied upon to establish the diagnosis of ulcerative colitis (UC) or Crohn disease (CD) or to distinguish between these 2 diseases. Saccharomyces cerevisiae IgA and IgG antibodies (ASCA) are most useful for distinguishing between UC and CD when assessed in conjunction with antineutrophil cytoplasmic antibodies (ANCA).


Some patients with CD have detectable ANCA, and some patients with UC have detectable IgA and/or IgG ASCA.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Rose NR, Mackay IR, eds: Inflammatory bowel diseases. In: The Autoimmune Diseases: Elsevier; 2008

2. Lichtenstein GR, Loftus EV, Isaacs KL, Regueiro MD, Gerson LB, Sands BE: ACG Clinical Guideline: Management of Crohn’s disease in adults. Am J Gastroenterol. 2018 Apr;113(4):481-517

3. Rubin DT, Ananthakrishnan AN, Siegel CA, Sauer BG, Long MD: ACG Clinical Guideline: Ulcerative colitis in adults. Am J Gastroenterol. 2019 Mar;114(3):384-413

4. Clark C, Turner J: Diagnostic modalities for inflammatory bowel disease: Serologic markers and endoscopy. Surg Clin North Am. 2015 Dec;95(6):1123-1141

5. Zhou G, Song Y, Yang W, et al: ASCA, ANCA, ALCA and many more: Are they useful in the diagnosis of inflammatory bowel disease? Dig Dis. 2016;34(1-2):90-97