PURPOSE:Perinuclear antineutrophil cytoplasmic autoantibody is known to be a marker for ulcerative colitis, and anti‐Saccharomyces cerevisiaeMannan antibody is a serologic marker associated with Crohn's disease. The aim of this study was to assess the value of detecting perinuclear antineutrophil cytoplasmic autoantibody and/or anti‐Saccharomyces cerevisiaeMannan antibody for the diagnosis of ulcerative colitis, Crohn's disease, Behçet's colitis, and tuberculous colitis.METHODS:Serum samples were obtained from 85 patients with Crohn's disease, 77 with ulcerative colitis, 36 with Behçet's colitis, 14 with tuberculous colitis, 20 healthy controls, and 21 first‐degree relatives of patients with Crohn's disease. Determination of perinuclear antineutrophil cytoplasmic autoantibody and anti‐Saccharomyces cerevisiaeMannan antibody was performed with the standardized indirect immunofluorescence technique and an enzyme‐linked immunosorbent assay, respectively.RESULTS:A relatively high percentage of patients with Crohn's disease (49.4 percent), relatives of Crohn's disease patients (61.9 percent), and patients with Behçet's disease (41.7 percent) tested seropositive for anti‐Saccharomyces cerevisiaeMannan antibody compared with normal controls (10 percent). In cases of ulcerative colitis, 44.2 percent tested seropositive for perinuclear antineutrophil cytoplasmic autoantibody, whereas the controls showed 0 percent positivity. The combination of a positive anti‐Saccharomyces cerevisiaeMannan antibody test and a negative perinuclear antineutrophil cytoplasmic autoantibody yielded a sensitivity and specificity of 48.2 and 87 percent, respectively, for Crohn's disease. The combination of a positive perinuclear antineutrophil cytoplasmic autoantibody test and a negative anti‐Saccharomyces cerevisiaeMannan antibody test yielded a sensitivity and specificity of 36.4 and 97.6 percent, respectively, for ulcerative colitis.CONCLUSION:Anti‐Saccharomyces cerevisiaeMannan antibody may be associated with Crohn's disease and Behçet's disease and perinuclear antineutrophil cytoplasmic autoantibody with ulcerative colitis. A combination of both tests may aid the differential diagnosis of inflammatory bowel disease.