Diagnostic utility of anti-Saccharomyces cerevisiae antibody (ASCA) and Interferon-? assay in the differential diagnosis of Crohn's disease and intestinal tuberculosis

Background: Differential diagnosis of Crohn's disease (CD) from intestinal tuberculosis (ITB) is challenging. Anti-Saccharomyces cerevisiae antibody (ASCA) is a specific serological marker for CD and INF-gamma assay (QuantiFERON-TB gold test, QFT) is a good supplementary diagnostic tool for ITB. We evaluated the clinical usefulness of ASCA and QFT for differential diagnosis of CD from ITB in Korean adults. Methods: A total of 147 patients suspected to have ITB or CD were prospectively enrolled from 13 hospitals. ASCA IgG and IgA serum titers were measured by ELISA, and the QFT test was also performed. Results: Thirty-two of 72 (44.4%) patients with CD were ASCA positive (titer > 25. U) compared to 10 of 75 ITB patients (13.3%) and 3 of 20 healthy controls (15%) (p< 0.01). The QFT test was positive in 7 patients with CD (9.7%) and 50 patients with ITB (66.6%) (p< 0.01). In cases which ASCA positive/QFT negative, the sensitivity, specificity, positive predictive value, and negative predictive value for the diagnosis of CD were 44.4%, 96.0%, 91.4%, and 64.3%, respectively. Conclusion: ASCA is a useful diagnostic tool for CD in Korea, where ITB is prevalent. In particular, when ASCA is combined with QFT, effective differential diagnosis of CD from ITB is possible.