Description of the blood test:

ASCA are immune proteins (antibodies) directed against a specific sugar (mannan) found in the cell wall of common baker’s or brewer’s yeast (Saccharomyces cerevisiae). While the yeast itself isn’t the cause of the disease, the presence of these antibodies reflects an abnormal immune response to common microbes in the gut. This occurs when the intestinal lining is damaged, allowing the immune system to “see” and attack these antigens.

What Does the Test Represent?

• Goal: To detect IgG and IgA antibodies against yeast mannan.
• Main Application: Differentiating between Crohn’s Disease and Ulcerative Colitis.
• Method: Enzyme-Linked Immunosorbent Assay (ELISA).

Collection Recommendations (General)

• Timing: Can be performed at any time of day.
• Fasting: Fasting for 8–12 hours is recommended for optimal results.
• Material: Venous blood (serum).
• Specific Rules: Inform your doctor if you are currently taking biological therapies or high-dose steroids, as these can sometimes affect antibody levels.

Factors Influencing the Result

• Diagnostic Pattern: ASCA is most useful when paired with the pANCA test.
  • ASCA (+) / pANCA (-): Strongly suggests Crohn’s Disease (about 80% predictive).
  • ASCA (-) / pANCA (+): Strongly suggests Ulcerative Colitis.
• Disease Severity: High levels of ASCA in patients with Crohn’s may predict a more aggressive disease course, including a higher risk of strictures (narrowing) or fistulas.
• Family History: ASCA can sometimes be found in healthy relatives of patients with Crohn’s Disease.

When to Take This Test?

• Recommendations: If you have chronic diarrhea, abdominal pain, weight loss, or rectal bleeding, and your doctor needs to determine the exact type of bowel inflammation.
• Importance: Since the surgical and medical treatments for Crohn’s and Ulcerative Colitis differ significantly, this “serological mapping” helps in choosing the right path.

Medical Interpretation

• Crucial Note: ASCA is not a “stand-alone” diagnostic tool. Only a specialist can “fine-tune” the diagnosis by comparing these results with a colonoscopy and biopsy.
• Positive Result: Highly associated with Crohn’s Disease.
• Negative Result: Does not rule out Crohn’s, as about 30–40% of Crohn’s patients are “ASCA-negative.”

Possible Further Investigations

• pANCA (Perinuclear Anti-Neutrophil Cytoplasmic Antibodies): The essential partner test for differential diagnosis.
• Calprotectin (Stool test): To measure the degree of active intestinal inflammation.
• Colonoscopy with Biopsy: The “gold standard” to see the inflammation directly.
• MRI or CT Enterography: To check for inflammation in the small intestine that a colonoscope cannot reach.
• Consultation with a Gastroenterologist.

When Does the Next Step Make Sense?

• If ASCA is positive, the next step is usually imaging (like an MRI or a colonoscopy) to confirm the location and extent of the inflammation. This allows the gastroenterologist to tailor the treatment—whether it be specific anti-inflammatory drugs, biologics, or dietary changes.
• All clinical decisions must be made by a healthcare professional based on the combination of laboratory, endoscopic, and clinical data.

👉 If necessary, you can discuss the analysis results with a specialist such as a gastroenterologist (Doctors – TAMC).