Test ID: IBDP    
Inflammatory Bowel Disease Serology Panel, Serum

As an adjunct in the diagnosis of ulcerative colitis and Crohns disease in patients suspected of having inflammatory bowel disease

The term "inflammatory bowel disease" (IBD) is often used to refer to 2 diseases, ulcerative colitis (UC) and Crohn's disease (CD), that  produce inflammation of the large or small intestines. The diagnosis of these 2 diseases is based on clinical features, the results of barium X-rays, colonoscopy, mucosal biopsy histology, and in some cases operative findings and resected bowel pathology and histology.

Recently, patients with IBD have been shown to have antibodies in serum that help to distinguish between CD and UC.(1) Patients with UC often have measurable neutrophil specific antibodies (NSA), which react with as yet uncharacterized target antigens in human neutrophils; whereas, patients with CD often have measurable antibodies of the IgA and/or IgG isotypes, which react with cell wall mannan of Saccharomyces cerevisiae strain Su 1.

Saccharomyces cerevisiae ANTIBODY, IgA

Negative: 0.0-20.0 U

Equivocal: 20.1-24.9 U

Weakly positive: 25.0-34.9 U

Positive: > or =35.0 U

Saccharomyces cerevisiae ANTIBODY, IgG

Negative: 0.0-20.0 U

Equivocal: 20.1-24.9 U

Weakly positive: 25.0-34.9 U

Positive: > or =35.0 U

NEUTROPHIL-SPECIFIC ANTIBODIES

Negative (not detectable)

The finding of neutrophil specific antibodies (NSA) with normal levels of IgA and IgG anti-Saccharomyces cerevisiae antibodies (ASCA) is consistent with the diagnosis of ulcerative colitis (UC); the finding of negative NSA with elevated IgA and IgG ASCA is consistent with Crohn's disease (CD).

NSA are detectable in approximately 50% of patients with UC, and elevated levels of either IgA or IgG ASCA occur in approximately 55% of patients with CD. Approximately 40% of patients with CD have elevated levels of both IgA and IgG ASCA.

Employed together, the tests for NSA and ASCA have the following positive predictive values (PV) for UC and CD, respectively: NSA positive with normal levels of IgA and IgG ASCA, PV of 91%; NSA negative with elevated levels if IgA and IgG ASCA, PV of 90%.(2)

Results from this test should not be exclusively relied upon to establish the diagnosis of ulcerative colitis (UC) or Crohn's disease (CD) or to distinguish between these 2 diseases. Some patients with CD have detectable neutrophil specific antibodies (NSA), and some patients with UC have elevated levels of IgA and/or IgG anti-Saccharomyces cerevisiae antibodies (ASCA).

Approximately one third of patients have low titered anti-nuclear antibodies (ANA), which make it impossible to distinguish the presence or absence of NSA. These results are reported as indeterminate.

Not useful to determine the extent of disease in patients with inflammatory bowel disease (IBD) or determine the response to disease-specific therapy including surgical resection of diseased intestine.

1. Sandborn WJ, Loftus EV Jr, Homburger HA, et al: Evaluation of serological disease markers in a population-based cohort of patients with ulcerative colitis and Crohn's disease. Inflamm Bowel Dis 2001 Aug;7(3):192-201

2. Homburger HA, Unpublished Mayo information

3. Vidrich A, Lee J, Janes E: Segregation of pANCA antigenic recognition by DNase treatment of neutrophils: ulcerative colitis, type 1 autoimmune hepatitis, and primary sclerosing cholangitis. J Clin Immunol 1995;Nov15(6):293-299