Use of serologic tests in Crohn's disease

Despite great progress in understanding and treating patients with Crohn's disease, the cause of this potentially debilitating disease remains elusive. Multiple studies support the hypothesis that patients with inflammatory bowel disease (IBD) have a dysregulated immune response to endogenous flora. Although we have only 2 labels for patients with IBD, Crohn's disease or ulcerative colitis (UC), these names fall short of describing the pathophysiology of these disease (Figure 1A). We now have a better understanding of the clinical, immunologic, and genetic heterogeneity that exists within "Crohn's diseases" and "ulcerative colitides." Mounting evidence suggests that IBD represents overlapping subgroups of inflammatory intestinal disorders along a continuum, with Crohn's disease and UC representing the extremes of this spectrum (Figure 1). Although the diagnosis of IBD continues to be based on clinical, endoscopic, histopathologic, and radiologic criteria, serologic markers can provide another tool to help diagnose and characterize patients with IBD. Their use is based on the hypothesis that the presence of these antibodies indicates the underlying dysregulated immune response and the environmental trigger, often bacterial, resulting in IBD (Figure 1B). This article will focus on the use of serologic tests to aid in the diagnosis and management of Crohn's disease (Table 1).