Wednesday, January 17, 2007

Blood tests for Crohn's and colitis blood tests and the link of altered gut flora in IBD.

What are Crohn's and colitis blood tests? Currently available blood tests utilized for the diagnosis of Crohn's disease and colitis include pANCA, anti-ASCA, anti-OmpC, and anti-CBir1 flagelin antibodies. Future blood tests will likely include antibodies against certain sugar (mannose) residues that are present in the cell wall of the yeast saccharomyces cerevisiae. Anti-Laminaribioside and anti-Chitiobioside antibodies are present in some Crohn’s patients who are anti-ASCA negative. Such tests will likely help further distinguish people with ulcerative colitis from Crohn's disease, a problem in about 10% of people with IBD.

What is pANCA antibody?
pANCA is peripheral anti-nuclear antibody. It is an antibody to protein in the nucleus of the cell. People with ulcerative colitis develop a positive pANCA frequently though it may be present in some people with Crohn's disease and rarely in normal people. The pANCA antibody has been further divided into subsets by Prometheus Laboratories Inc. Neutrophil-specific pANCA ELISA (NSNA) is positive in the majority of people with ulcerative colitis (UC) and a small subset of people with Crohn’s disease that have disease more like UC. Immunofluorescent cellular staining of neutrophils (NSNA IFA) and enzyme Dnase testing (NSNA DNase sensitivity) is also done as part of the Prometheus IBD Serology 7. When the latter is present in high levels it is significantly associated with development of inflammation of the rectal pouch (pouchitis) created when someone has entire colon removed for ulcerative colitis that does not respond to medical treatment.

What is the ASCA antibody for Crohn’s disease?
ASCA is anti-saccharomyces cerevisiae antibody. Saccharomyces cerevisiae is Brewer’s or Baker’s yeast. Crohn’s patients have high prevalence of increased blood levels of antibody to this yeast. A few people with celiac disease have this antibody present in their blood in the absence of signs of Crohn’s disease.

What is OmpC antibody?
OmpC is the abbreviation for outer membrane C for the antibody to the outer membrane of the Escherechia coli bacteria that develops in many Crohn’s patients though the E. coli bacteria is not thought to be the cause of Crohn’s disease.

What is anti-CBir1 antibody?
Prometheus Laboratories has only recently added this antibody test. It is an antibody to the flagella protein on bacteria that enables movement and attachment of the bacteria in the intestine. When the anti-CBir1 antibody is present in high levels, especially when ASCA and/or OmpC are also present, Crohn’s disease is present. When present at high levels associated with one the pANCA patterns, it is associated with Crohn’s colitis more commonly than ulcerative colitis. It however can be present but not particularly elevated in UC when UC pattern of pANCA is also noted.

How these tests are helpful: If you have a diagnosis of ulcerative colitis or Crohn’s disease these blood tests may be very helpful in your treatment as they predict severity, complications, risks of surgery and response to various treatments. If you have unexplained abdominal pain, diarrhea, blood in your stools then these tests should be considered as if they are all negative then Crohn's disease or ulcerative colitis are unlikely. However, if one or more are present you need a colonoscopy. Since the antibodies detected are primarily against protein products of bacteria and dietary yeast their presence, especially in Crohn's diasease are consistent with the growing belief that altered levels of gut microorganisms or gut flora are critical in teh development of IBD. It also supports the observation that antibiotics and probiotics help many IBD patients and may prevent onset of IBS after gut infection. Stay tuned for more on our journey with the Food Doc.


Abreu MT et al. Use of Serologic Tests in Crohn’s Disease. Clinical Gastroenterology and Hepatology. Vol.4, No. 3. 2001

Dotan I et al. Antibodies Against Laminaribioside and Chitiobioside Are Novel Serologic Markers in Crohn’s Disease. Gastroenterology. Vol.131, No. 2. 2006

Mei, L et al. Familial Expression of Anti-Escherichia coli Outer Membrane Porin C in Relatives of Patients with Crohn’s Disease. Gastroenterology. Vol. 130, No. 4 2006

Stadaert-Vitse et al. Candida albicans Is an Immunogen for Anti-Saccharomyces cerevisiae Antibody Markers of Crohn’s Disease. Gastroenterology. Vol 130, No. 6. 2006

Targan, SR et al. Antibodies to Cbir1 Flagelin Define a Unique Response That Is Associated Independently Crohn’s Disease. Gastroenterology. Vol.128, No.7. 2005

Crohn’s and Colitis Foundation of America (CCFA)
Prometheus Laboratories Inc.
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