Anti-Saccharomyces cerevisiae antibody does not differentiate between Crohn's disease and intestinal tuberculosis

The clinical, morphological, and histological features of intestinal tuberculosis (IT) and Crohn's disease (CD) mimic so much, that it becomes difficult to differentiate between them. The sensitivity of anti-Saccharomyces cerevisiae antibody (ASCA) IgG and ASCA IgA in CD is 60%-80%, whereas the specificity is almost 90%. There are no reports of study of ASCA in patients with IT, nor has it ever been used to differentiate CD from IT. Patients with ulcerative colitis (UC; n=25), CD (n=59), and IT (n=30) and 21 healthy controls were included in this study. The location and behavior of CD were classified according to the Modified Montreal classification. Five milliliters of blood was taken from them and serum was stored at -70 degrees C. ASCA antibodies (both IgG and IgA) were estimated using commercially available ELISA kits (AESKU Diagnostics, Germany). Anti-neutrophilic cytoplasmic antibody was measured by indirect immunofluorescence test. ASCA IgA was positive in 4.7%, 28%, 33.9%, and 43.3% and ASCA IgG was positive in 4.7%, 24%, 50.8%, and 46.6% of healthy controls and patients with UC, CD, and IT, respectively. Either ASCA IgG or ASCA IgA was positive in 9.5%, 40%, 61% and 66.6% of healthy controls, UC, CD, and IT, respectively. ANCA was positive in 0%, 32%, 10.1%, and 6.6% of healthy controls, UC, CD, and IT, respectively. ASCA IgG was positive in a significantly higher number of patients with CD (P<0.0001) and IT (P<0.0001) in comparison to healthy controls. ASCA IgA was positive in a significantly higher number of patients with UC (P<0.04), CD (P<0.013), and IT (P<0.006) in comparison to healthy controls. In comparisons between diseases, ASCA IgG was positive in significantly more patients with CD (P<0.001) and IT (P<0.001) in comparison to UC. There was no significant difference in ASCA IgA (33.9% vs. 43.3%), ASCA IgG (50.86% vs. 46.6%), or ANCA (10.7%, 7.4%) in patients with CD and IT, respectively. There was no correlation between ASCA and duration, location and behavior of CD, and IT. We conclude that ASCA IgG and ASCA IgA do not help to differentiate between IT and CD.