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ASCA - Anti-Saccharomyces Cerevisiae Antibodies Test

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ASCA - Anti-Saccharomyces Cerevisiae Antibodies Test

-The ASCA test, or Anti- Saccharomyces cerevisiae Antibodies test, is part of the IBD testing panel, Prometheus IBD sgi Diagnostic used to help differentiate between UC (Ulcerative Colitis) and CD (Crohn's Disease).

-Although the ASCA test is not a definitive marker for discriminating between UC and CD alone, a positive ASCA test is associated with cases of Crohn's disease (59%-63%). The ASCA test should not be the only indicator of Crohn's disease as 13.7% or Ulcerative Colitis patients exhibit positive ASCA tests, as well as 21% of unaffected Crohn's patient family members.
- A separate study indicated ASCA was positive in 44% of Crohn's patients and 0% Ulcerative Colitis patients. [5]

- ASCA can be used to support a diagnosis of IBD or as an aid in distinguishing UC from CD but should not be used to diagnose IBD

- A positive ASCA correlates with the presence of small bowel involvement as with well as fibrostenosing and perforating disease.[4]

ASCA Sensitivity and Specificity

The Sensitivity and Specificity of ASCA for predicting Crohn's Disease are 57% and 87%, respectively.[4]

However, the ASCA Diagnostic Test will typically look for two different classes of Antibodies, Immunoglobulin A (IgA) and Immunoglobulin G (IgG).

If either the IgA or IgG class of Antibody are analyzed using Indirect Immunofluorescence, (varies by Laboratory)[8],
  • The Sensitivity ranges between:
    (IgA) 41% - 61%;
    (IgG) 41% - 75%
  • The Specificity ranges between
    (IgA) 88% - 95%;
    (IgG) 88% - 96%

If both IgA and IgG classes of ASCA Antibodies are analyzed together using Indirect Immunofluorescence (varies by Laboratory)[8],
  • The Sensitivity ranges between:
    (IgA and IgG) 30% - 53%
  • The Specificity ranges between
    (IgA and IgG) 97% - 98%

However, if both IgA and IgG classes of ASCA Antibodies are analyzed together using BOTH Enzyme Linked Immunosorbant Assay (ELISA) and Indirect Immunofluorescence (IIF), the Sensitivity decreases and Specificity approaches 100% (varies by Laboratory)[8],
  • The Sensitivity ranges between:
    (IgA and IgG) 23% - 38%
  • The Specificity ranges between
    (IgA and IgG) 99% - 100%

What does a positive ASCA test mean?

-The ASCA tests for the presence of antibodies (part of the immune system) that are specific for a type of yeast, Saccharomyces cerevisiae.

- Patients that test positive for the ASCA antibody have a higher rate of disease in the ileum (or ileum and right colon) than ASCA-negative patients (58% versus 18%).[5]

- Patients that test positive for ASCA antibody have a higher incidence of needing ileocecal resection (36% versus 13%).[5]

References

1. Gologan S, Iacob R, Preda C et al. Higher titers of Anti-Saccharomyces cerevisiae Antibodies IgA and IgG are Associated with More Aggressive Phenotypes in Romanian Patients with Crohn’s Disease. J Gastrointestin Liver Dis 2012;21(1):39.44. http://www.jgld.ro/2012/1/8.pdf

2. Papp M, Altorjay I, Norman GL, et al. Seroreactivity to microbial components in Crohn’s disease is associated with ileal involvement,noninflammatory disease behavior and NOD2/CARD15 genotype, but not with risk for surgery in a hungarian cohort of IBD patients. Inflamm Bowel Dis. 2007;13(8):984-992. http://onlinelibrary.wiley.com/doi/1.../ibd.20146/pdf

3. Vermeire, S. et al. 2001. Anti-Saccharomyces cerevisiae antibodies (ASCA), phenotypes of IBD, and intestinal permeability: a study in IBD families. Inflamm. Bowel Dis. Feb;7(1):8-15.

[pos]4a[/pos]4. Walker LJ, Aldhous MC, Drummond HE, Smith BRK, Nimmo ER, Arnott IDR, Satsangi J. Anti-Saccharomyces cerevisiae antibodies (ASCA) in Crohn's disease are associated with disease severity but not NOD2/CARD15 mutations. Clinical & Experimental immunology. 2004; 135(3): 490-496. http://onlinelibrary.wiley.com/doi/1...03.02392.x/pdf

5. Zholudev A, Zurakowski D, Young W, Leichtner A and Bousvaros A. Serologic Testing with ANCA, ASCA, and Anti-OmpC in Children and Young Adults with Crohn's Disease and Ulcerative Colitis: Diagnostic Value and Correlation with Disease PhenotypeDiagnostic Value and Correlation with Disease Phenotype. The American Journal of Gastroenterology. 2004; 99:2235-2241.

6. Amre D, Lu S-E, Costea F, and Seidman EG. Utility of serological markers in predicting the early occurrence of complications and surgery in pediatric Crohn's disease patients. Am J Gastroenterol. 2006;101(3): 645–652.



8. Klebl FH, Bataille F, Hofstadter F, Herfarth H, Scholmerich J, Rogler G. Optimising the diagnostic value of Anti-Saccharomyces cerevisiae antibodies (ASCA) in Crohns disease. Int J Colorectal Dis. 2004; 19:319–324 http://www.springerlink.com/content/...r/fulltext.pdf

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