A positive Saccharomyces cerevisiae IgG (ASCA) indicates the immune system has produced antibodies to S. cerevisiae. It's commonly linked with Crohn’s disease and can help distinguish Crohn’s from ulcerative colitis, suggesting small‑bowel involvement or a more aggressive course. It is not diagnostic alone; results need correlation with symptoms, endoscopy, imaging and other tests because false positives/negatives can occur.

Anti‑Saccharomyces cerevisiae antibodies (ASCA) are immune proteins (IgA and IgG) targeting the cell‑wall mannan of the yeast Saccharomyces cerevisiae. They serve as serologic markers more often positive in Crohn’s disease than ulcerative colitis, can support diagnosis and suggest a more complicated disease course, but are not diagnostic alone and must be interpreted with clinical, endoscopic, and imaging findings.

Anti‑Saccharomyces cerevisiae antibodies (ASCA), particularly ASCA‑IgA and ASCA‑IgG, are commonly positive in Crohn’s disease and can help distinguish it from ulcerative colitis. By contrast, p‑ANCA is more often associated with ulcerative colitis and tends to be negative in Crohn’s. ASCA has moderate sensitivity and specificity and is used alongside clinical findings and imaging for diagnosis.

ASCA antibodies are frequently positive in Crohn's disease, more often than in ulcerative colitis or healthy people. Sensitivity is moderate (many patients are negative) but specificity is higher, so positivity supports—but does not confirm—a Crohn's diagnosis. Combined IgA/IgG testing and higher titres associate with small-bowel involvement and complicated disease, guiding evaluation alongside clinical, endoscopic, and imaging findings.

Saccharomyces cerevisiae is generally beneficial: used in baking, brewing and some probiotic preparations to support digestion and reduce antibiotic‑associated diarrhea. However, it can be harmful in rare cases—especially for people with weakened immune systems or indwelling catheters—where it may cause bloodstream infection or allergic reactions. Consult a clinician before probiotic use if immunocompromised or critically ill.

A positive IgG antibody test usually indicates past exposure or prior vaccination and that your immune system developed antibodies. It does not necessarily mean current active infection or guaranteed immunity; protection’s strength and duration vary. False positives can occur. Your clinician will interpret results alongside symptoms and history, and may recommend PCR or additional/confirmatory testing if needed.