The Anti-Saccharomyces Cerevisiae Antibody Assay in a Province-Wide Practice: Accurate in Identifying Cases of Crohn’s Disease and Predicting Inflammatory Disease

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To determine the utility of the anti-Saccharomyces cerevisiae antibody (ASCA) ELISA test developed in Manitoba in 2001 in a population-wide sample referred from physicians across Manitoba in their investigation of patients with gastrointestinal symptoms. Patients whose serum was referred for ASCA testing in 2001 and 2002 were eligible for the present study. ELISA was performed by a technologist, blind to patient diagnoses. A single investigator contacted physicians to facilitate chart review. Data collected included demographics, final diagnoses and tests used to substantiate the final diagnosis. Of 482 subjects identified, 410 charts were available for review and 29 of those were unavailable for follow-up or had incomplete charts. The present study population included Crohn's disease (CD, n=114), ulcerative colitis (n=74), indeterminate colitis (n=31), celiac disease (n=9), irritable bowel syndrome (n=75), other diagnoses (n=33) and no disease (n=45). ASCA had a sensitivity of 37% (95% CI 27.8 to 46.8) and specificity of 97% (95% CI 93.8 to 98.6) for diagnosing CD and an odds ratio for a diagnosis of CD of 18.4 (95% CI 8.2 to 41.3). The 47 ASCA-positive patients included the following diagnoses: CD=39, ulcerative colitis=3, indeterminate colitis=1, celiac disease=3 and no disease=1. The likelihood of having an inflammatory disease if ASCA is positive was nearly 40-fold. A positive ASCA test using this assay nearly clinches a diagnosis of some form of inflammatory intestinal disease, which is highly likely to be CD. In symptomatic patients, a positive ASCA test should encourage the clinician to pursue further investigations.