Inflammatory bowel disease (IBD) is a general term used to describe diseases that cause inflammation of the intestines. Crohn’s disease (CD) and ulcerative colitis (UC) are the two major IBDs. In Crohn’s disease, inflammation usually occurs in the lower part of the small intestine (distal ileum), but may affect any part of the digestive tract. The inflammation in Crohn’s disease extends deep into the affected tissue, in contrast to UC, which causes inflammation and ulcers in the top layers of the lining of the colon and rectum. Inflammation in CD is asymmetrical and segmental, with areas of both healthy and diseased tissue, in contrast to UD where inflammation is symmetrical and uninterrupted from the rectum proximally.
Both CD and UC are chronic, and affect men and women on an approximately equal basis. These diseases are seen most commonly in northern Europe and North America. Approximately 20 percent of individuals with CD have a blood relative with some form of IBD. The onset of CD is usually between ages 15 and 30 with a second smaller peak of incidence between 50 and 70. Over the past decade, several reports have noted an increase in the prevalence of CD in various geographic regions. Although there are many theories concerning the cause of CD and UC, none have been proven. Since many of the symptoms of CD and UC are similar, diagnosis is often difficult, time consuming, and invasive. Approximately 10-12 percent of cases is not initially classifiable and is referred to as "indeterminate colitis." Over time, about half of these patients are eventually classified as CD or UC.
Anti-Neutrophil Cytoplasmic Antibody (ANCA) and Anti-Saccharomyces Cerevisiae Antibody (ASCA) have been investigated as techniques to improve the efficiency and accuracy of diagnosing IBD in order to potentially decrease the extent of the diagnostic work-up or to avoid invasive diagnostic imaging. Testing for ANCA is available in most clinical laboratories. ASCA is more recently developed and may not be widely available, but the reliability of testing for ASCA among different labs may be more variable as compared to ANCA. These serum antibodies have several potential uses. As a diagnostic test, they might also be useful in differentiating between UC and CD in cases of indeterminate colitis. A second potential use is to classify subtypes of IBD by location of disease (i.e. proximal versus distal bowel involvement) or by disease severity, thereby providing prognostic information. It has also been proposed that these markers may predict response to anti-tumor necrosis factor (TNF) therapy or identify susceptibility to IBD among family members of an affected individual (see medical policy MED207.153).
Clinical management of Crohn’s disease and ulcerative colitis requires repeated assessments; endoscopy with histological examination remains the gold standard for detecting and quantifying intestinal inflammation. Several laboratory tests have been studied but to date, a disease marker is not yet available. In recent years, research has drawn attention to fecal markers owing to their specificity for intestinal inflammation, ease of sample collection, availability of commercial immunoassays and convenience. These biologic markers have been used to assess inflammatory bowel disease patients for the purposes of their clinical management and response to treatment.
Prometheus® Laboratories Inc. (San Diego, CA) offers a variety of proprietary diagnostic tests for a variety of disorders, including one for the diagnosis of inflammatory bowel disease (IBD). The IBD First Step™ and IBD Diagnostic System tests are frequently requested by providers as "Prometheus Testing." Prometheus® IBD sgi Diagnostic™ includes the serological markers ASCA immunoglobulin A (IgA), ASCA immunoglobulin G (IgG), ANCA IgG, perinuclear anti-neutropholic cytoplasmic antibody (pANCA), DNAse pANCA, anti-outer membrane porin C (anti-OmpC), anti-CBir1 flagellin (anti-CBir1), Fla-X flagellin, and A4-Fla2 flagellin.