Anca

Clinical Chemistry 52:2 171–181 (2006)

Review

Serologic Markers in Inflammatory Bowel Disease
Xavier Bossuyt
Inflammatory bowel disease (IBD) is an enduring disease involving mostly young people, with symptoms of bloody diarrhea and abdominal cramps. Several antibodies have been associated with IBD, the 2 most comprehensively studied being autoantibodies to neutrophils (atypicalperinuclear anti-neutrophil cytoplasmic antibodies) and anti-Saccharomyces cerevisiae antibodies. This review focuses on the value of these antibodies for diagnosing IBD, differentiating Crohn disease from ulcerative colitis, indeterminate colitis, monitoring disease, defining clinical phenotypes, predicting response to therapy, and as subclinical markers. Pancreatic antibodies and newly identifiedanti-microbial antibodies (anti-outer membrane porin C, anti-I2, and anti-flagellin) are also reviewed.
© 2006 American Association for Clinical Chemistry

romyces cerevisiae antibodies (ASCAs). This review summarizes the current knowledge about the putative clinical value of these 2 antibodies in IBD. Pancreatic antibodies and newly identified anti-microbial antibodies (anti-outer membrane porin C,anti-I2, and anti-flagellin) are also reviewed.

Clinical Presentation and Diagnosis of IBD
CD patients may present with almost any gastroenterologic symptom depending on the site of the disease. Colonic disease (either alone or together with small intestine) is more common than disease in the terminal regions of the ileum or cecum and usually presents with chronic abdominal pain and diarrhea.In more severe forms, a mass may be present in the right iliac fossa. Patients with CD can have typical perianal lesions, such as ulcers or multiple fistulas. In CD, serum concentrations of C-reactive protein (CRP) correlate well with disease activity and with other markers of inflammation as the CD activity index (2 ). Increased CRP ( 45 mg/L) in patients with IBD predicts with a high certaintythe need for colectomy (2 ). Patients with UC suffer from bloody diarrhea or rectal bleeding and tenesmus because of the rectal involvement. There are several structural differences between CD and UC (3 ). In UC, the disease is restricted to the rectum and colon. The lesions are continuous and restricted to the mucosa. There is muscular thickening, mucin depletion, and glandular damage. In CD, thedisease may affect any part of the gastrointestinal tract. The lesions are discontinuous and transmural (fissure, abscess, fistula). There may be fibrosis (stenosis) and lymphoid ulcers. Histiocytic granulomas are the hallmark of CD, but are found in only 60% of cases. Diagnosis of IBD and differentiation between CD and UC can be made accurately in most patients based on the patient’s history andphysical examination, ileocolonoscopic examination, biopsy, double-contrast barium enema examination, and microbiology. The differential diagnosis includes irritable bowel disease; infective
1 Nonstandard abbreviations: IBD, inflammatory bowel disease; CD, Crohn disease; UC, ulcerative colitis; P-ANCA, perinuclear anti-neutrophil cytoplasmic antibody; ASCA, anti-Saccharomyces cerevisiae antibody;CRP, C-reactive protein; BPI, bactericidal permeability increasing; and HMG, highmobility group.

Inflammatory bowel disease (IBD)1 embodies a spectrum of disorders that affect the gastrointestinal tract, the 2 major entities being Crohn disease (CD) and ulcerative colitis (UC). IBD is a lifelong disease involving mostly young people, often in a severe way. Although the etiology of IBD isunknown at present, it is believed to be an immunologically mediated disease in a genetically susceptible host. The picture that emerges is that IBD results from an aberrant immune response and loss of tolerance to the normal intestinal flora, leading to chronic inflammation of the gut. This idea is supported by the occurrence of antibodies directed to microbial antigens (see below) and by the...