ASCA (anti-Saccharomyces cerevisiae) – IgA and IgG

Indication

Suspicion of Crohn’s disease.

Method

ELISA with mannan from Saccharomyces cerevisiae as antigen.

Answer

The result is given as a ratio between patient serum and normal serum.

Interpretation

IgA antibodies against Saccharomyces cerevisiae (ASCA) occur in patients with Crohn’s disease in 60-75% but are rare in patients with ulcerative colitis. IgG ASCA also often occurs together with IgA ASCA but some patients have only one Ig class. The antigen is oligomannos epitopes from the cell wall of ordinary yeast (Saccharomyces cerevisiae). Patients with ulcerative colitis (UC) have ANCA of the so-called P-ANCA type (also called atypical ANCA). The antigens are unknown but they may be elastase, lactoferrin, BPI etc. The combination of ASCA and ANCA is therefore used to distinguish UC from Crohn’s disease, as a typical UC patient has ANCA, whereas a typical Crohn’s patient has ASCA.

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