Effects of disease activity on anti–Saccharomyces cerevisiae antibodies. Implications for diagnosis and follow‐up of children with Crohn's disease

Background: To determine diagnostic accuracy of anti–Saccharomyces cerevisiae antibodies (ASCA) in identifying children with inflammatory bowel disease (IBD) and to differentiate Crohn's disease (CD) from other IBD forms; and to determine the effect of medical or surgical treatment and of disease location and activity on ASCA titers. Methods: Serum samples were obtained from 196 IBD children and 142 controls. ASCA IgA and IgG titers were measured by ELISA. Measurements were repeated during the follow up of CD children. Results: ASCA titers were significantly higher in CD than in other IBD and in control patients. Combination of IgA and IgG ASCA positivity was highly specific for CD. Medical treatment and disease location did not influence assay results. Significantly lower ASCA titers were obtained in CD children with intestinal resection compared to CD‐affected children who did not undergo surgical resection. ASCA titers correlated significantly with disease activity, and children with severe active disease showed higher ASCA values compared to those in remission. A signficant reduction of ASCA was observed during the follow‐up of CD children when clinical remission was achieved. Conclusions: The diagnostic accuracy of ASCA is influenced by disease activity and this suggests an additional use for the follow‐up of CD children of this assay.