ASCA-IgA Saccharomyces Cerevisiae

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IgA antibody against yeast antigens.

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ASCA-IgA Saccharomyces Cerevisiae Test Information Guide

Why is it done?
- Detects IgA antibodies against Saccharomyces cerevisiae (baker's yeast), which are markers of immune response to yeast antigens
- Aids in diagnosis of inflammatory bowel disease (IBD), particularly Crohn's disease, where it serves as a serological marker
- Helps distinguish between Crohn's disease and ulcerative colitis, as ASCA is more commonly positive in Crohn's disease
- Ordered when patients present with symptoms suggestive of IBD such as chronic diarrhea, abdominal pain, rectal bleeding, and weight loss
- Used as part of a comprehensive serological panel (often combined with pANCA, ASCA-IgG, and other markers) for IBD assessment
- Typically performed during initial IBD workup or when disease status needs clarification
Normal Range
- Normal (Negative): <1.0 Unit (or <1.0 EU/mL depending on laboratory) - indicates absence of IgA antibodies to Saccharomyces cerevisiae
- Borderline: 1.0-1.5 Units - results in this range may require repeat testing or clinical correlation
- Positive (Abnormal): >1.5 Units (or >1.5 EU/mL) - indicates presence of IgA antibodies to yeast and is associated with IBD, particularly Crohn's disease
- Units of Measurement: ELISA Units (EU/mL) or optical density units - varies by laboratory method and assay platform
- Reference ranges may vary between laboratories; always refer to the specific laboratory report for interpretation guidelines
- Negative result suggests low probability of Crohn's disease but does not completely exclude it, as approximately 40-60% of Crohn's patients test positive
Interpretation
- Positive ASCA-IgA Result: Suggests presence of abnormal immune response to yeast antigens; strong association with Crohn's disease, present in 40-60% of Crohn's patients and up to 10% of ulcerative colitis patients
- Negative ASCA-IgA Result: Does not exclude IBD diagnosis; approximately 40-50% of Crohn's disease patients test negative; may support diagnosis of ulcerative colitis over Crohn's disease when combined with other serological markers
- Clinical Significance with Other Markers: ASCA-IgA combined with pANCA (perinuclear anti-neutrophil cytoplasmic antibodies) improves diagnostic accuracy; ASCA+/pANCA- pattern strongly suggests Crohn's disease; ASCA-/pANCA+ pattern more consistent with ulcerative colitis
- Risk Stratification: ASCA positivity may indicate more severe disease phenotype with higher risk of complications such as strictures, fistulas, and need for surgery
- Factors Affecting Results: Antibiotic use may alter antibody titers; disease activity can influence antibody levels; test remains positive even during remission; genetic predisposition influences antibody production
- Longitudinal Monitoring: ASCA-IgA titers generally remain stable over time in IBD patients; may increase with disease flares or disease progression
- Distinguishing IBD from Non-IBD: Positive ASCA-IgA in context of chronic GI symptoms helps differentiate IBD from irritable bowel syndrome (IBS) and other functional disorders
Associated Organs
- Primary Organ System: Gastrointestinal tract, specifically small and large intestines where chronic inflammation occurs in IBD
- Crohn's Disease: Chronic inflammatory condition affecting entire GI tract from mouth to anus; associated abnormal ASCA-IgA indicates higher risk of transmural inflammation, penetrating disease, and fistula formation
- Ulcerative Colitis: Limited to colon and rectum; ASCA-IgA typically negative though may be positive in subset of patients with overlapping phenotype
- Associated Complications: Strictures causing bowel obstruction, fistulas, perforations, toxic megacolon, malabsorption with nutritional deficiencies, anemia from chronic blood loss
- Extraintestinal Manifestations: Joint involvement (arthritis), skin conditions (erythema nodosum, pyoderma gangrenosum), eye inflammation (uveitis), liver disease (primary sclerosing cholangitis), with ASCA positivity correlating to increased risk
- Secondary Organ Involvement: Pancreas (pancreatitis), biliary system, musculoskeletal system, and ocular tissues may be affected in severe or complicated IBD with abnormal serology
- Immune System: Involves mucosal and systemic immune response dysregulation; ASCA-IgA reflects aberrant antibody production by B cells in gut-associated lymphoid tissue
- Risk of Colorectal Cancer: Long-standing ASCA-positive Crohn's disease associated with increased cancer risk requiring surveillance colonoscopy
Follow-up Tests
- pANCA (Perinuclear Anti-Neutrophil Cytoplasmic Antibody): Complementary serology marker; typically negative in Crohn's disease but positive in ulcerative colitis; should be ordered simultaneously with ASCA-IgA for complete serological assessment
- ASCA-IgG: IgG antibodies to Saccharomyces cerevisiae; provides additional serological information; ASCA-IgG positivity may have different prognostic significance than IgA
- Anti-Infliximab (ATI) and Anti-Adalimumab (AAA) Antibodies: If biologic therapy initiated; useful for monitoring immunogenicity to TNF-inhibitor medications
- Inflammatory Markers: Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) to assess degree of inflammation; elevated in active disease
- Fecal Calprotectin: Non-invasive marker of intestinal inflammation; correlates with disease activity; useful for monitoring and distinguishing organic from functional GI disease
- Complete Blood Count (CBC): Assess for anemia from chronic blood loss, leukocytosis from inflammation, thrombocytosis from acute phase response
- Comprehensive Metabolic Panel: Assess albumin and nutritional status, liver and kidney function, electrolytes for disease complications
- Colonoscopy with Biopsy: Gold standard for IBD diagnosis; performed to visualize mucosa, assess extent and severity of inflammation, obtain histological confirmation
- CT Enterography or MR Enterography: Imaging studies to assess full extent of disease, detect complications like strictures, fistulas, and penetrating disease
- Upper Endoscopy (EGD): If symptoms or positive ASCA suggest involvement of upper GI tract; important in Crohn's disease which can affect entire GI tract
- Monitoring Frequency: ASCA-IgA typically does not require serial monitoring; reorder only if clinical status changes significantly or if diagnostic uncertainty exists
- Other Serological Markers: Anti-OmpC, anti-Cbir1 antibodies may be considered in specialized centers for additional disease phenotyping and prognostication
Fasting Required?
- Fasting Required: NO - ASCA-IgA is a serological antibody test that does not require fasting; food and fluid intake do not affect test results
- Patient Preparation: Routine blood draw preparation; patients may eat and drink normally before test; no special dietary restrictions needed
- Medications: No medications need to be held or avoided before ASCA-IgA testing; immunosuppressive or biologic medications do not interfere with antibody detection
- Collection Details: Single blood draw via venipuncture into appropriate collection tube (typically serum separator tube); approximately 5 mL of blood needed
- Timing: Test can be performed at any time of day without regard to meal timing or circadian considerations
- Practical Instructions: Patients should wear comfortable clothing allowing easy access to arm for venipuncture; inform phlebotomist of any history of difficult blood draws or needle anxiety
- Post-Collection: No special post-test restrictions; patients may resume normal activities immediately; minimal risk of complications with routine venipuncture

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