Special remarks:

ASCA is an indirect solid phase enzyme immunoassay (ELISA) for the quantitative measurement of IgG and IgA class autoantibodies against mannan from Saccharomyces cerevisiae in human serum or plasma. The assay is intended for in vitro diagnostic use only as an aid in the diagnosis of Crohn´s disease.

Accurate diagnosis of inflammatory bowel disease (IBD), in particular the differentiation between the two major IBDs ulcerative colitis and Crohn´s disease, is important for treatment and prognosis. Ulcerative colitis is characterized by an inflammation and ulcers in the top layers of the lining of the colon and rectum. Crohn´s disease shows a wide spread inflammation of the gastro-intestinal tract with granuloma formation extending deep into the affected tissue. Inflammation in Crohn´s disease is asymmetrical and segmental, with areas of both healthy and diseased tissue, in contrast to ulcerative colitis where inflammation is symmetrical and uninterrupted from the rectum proximally.

To differentiate between Crohn´s disease and ulcerative colitis the detection of ANCA (Anti Neutrophil Cytoplasmic Antibody) and ASCA (Anti-Saccharomyces cerevisiae antibody) can be used. ASCA are directed against oligomannosidic epitopes on the cell wall mannan (phosphopeptidomannan) of the yeast Saccharomyces cerevisiae. IgG as well as IgA ASCA show a specificity of 95-100% for Crohn´s disease. ASCA are strongly associated to Crohn´s disease. Studies showed 5% positive IgG and 7% IgA class ASCA in ulcerative colitis whereas in Crohn´s disease a sensitivity of 75% for IgG and 60% for IgA class ASCA could be observed.

The occurence of atypical ANCA (aANCA) in Crohn´s disease is more infrequent than in ulcerative colitis. The prevalence of ANCA varies from 50% to 90% in ulcerative colitis and 10% to 20% in Crohn´s disease.

The combination of both serological tests makes possible a rapid and non-invasive differential diagnosis between Crohn´s disease and ulcerative colitis.