Clinical Information

Inflammatory bowel disease (IBD) refers to 2 diseases, ulcerative colitis (UC) and Crohn disease (CD, regional enteritis), both of which result from chronic inflammation in the gastrointestinal (GI) tract.(1) CD is characterized by chronic diarrhea, abdominal pain, and fatigue.(2) In comparison, UC frequently presents with bloody diarrhea that is of an urgent nature.(3) Inflammation in UC most frequently affects the rectum and proximal colon, and presents with continue mucosal involvement. In CD, inflammation can affect almost any area of the GI tract and is usually evidenced as patchy, transmural lesions.

Diagnosis of IBD is primarily based on clinical evaluation, endoscopy with biopsy, and imaging studies.(4) Because CD and UC are characterized by GI inflammation, fecal calprotectin can be used to differentiate IBD from noninflammatory conditions such as irritable bowel syndrome (IBS). Fecal calprotectin is useful in excluding IBD as a diagnosis and avoiding unnecessary endoscopic or imaging procedures.

CD and UC are associated with the presence of various antimicrobial and autoantibodies.(5) Patients with UC often have measurable antineutrophil cytoplasmic antibodies (ANCA), which react with as yet uncharacterized target antigens in human neutrophils; in contrast, patients with CD often have measurable IgA and/or IgG antibodies, which react with cell wall mannan of Saccharomyces cerevisiae. Despite these associations, current guidelines indicate that testing for these antibodies is not sufficiently sensitive for use in the diagnosis of IBD.(2,3) Rather, these antibodies should be limited to distinguishing between CD and UC in cases where the specific diagnosis is unclear based on pathologic and imaging studies.