Scot M. Lewey, DO, FACG, FASGE, AGAF
Clinical Professor of Medicine
Serology is a term for blood tests. The term serologic marker simply means the presence of specific blood test believed to be highly indicative of the presence of a particular disease. IBD serologic markers or serology is the testing of blood for the presence of antibodies in the blood that indicate the likelihood of presence or absence of ulcerative colitis or Crohn’s disease.
Prometheus Laboroatories has released a new IBD panel termed sgi that includes the previously available blood tests but adds additional antibody markers, genetics for Crohn's disease and levels of inflammatory markers.
Already available were pANCA, ASCA, OMPc, and CBir1 flagelin. pANCA is an abbreviation for peripheral anti-cytoplasmic antibody. ASCA is short for anti-sacchromyces cerevisiae antibody, OmpC for outer membrane porin protein and CBir1 flagelin is an antibody to a specific protein on bacteria that constitutes the flagelin or hair like structure enabling movement and attachment of bacteria in the intestine.
Certain antibody patterns are highly predictive of presence of IBD, specifically either Crohn’s disease or ulcerative colitis. The patterns also may be predictive of involvement of small intestine, risk of scarring resulting in bowel obstruction (fibrostenosis) or perforation.
Yes, the presence of the antibodies is not diagnostic for colitis or Crohn’s disease. However, the presence of the antibodies is probably not normal and indicates some increased gut permeability due to injury that may be predictive of risk for these conditions if the gut permeability is not reversed or altered gut bacteria not resolved.
pANCA is an abbreviation for peripheral anti-nuclear antibody. The pANCA antibody is divided into subsets. 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 characteristics more like UC. Immunofluorescent cellular staining of neutrophils (NSNA IFA) and enzyme Dnase testing (NSNA DNase sensitivity) are part of the Prometheus IBD Serology 7. When the latter is present in high levels there is a significantly increased risk of development of inflammation of the rectal pouch (pouchitis) in patients who undergo colon removal for ulcerative colitis that has not responded to medical treatment.
ASCA is anti-saccharomyces cerevisiae antibody. Saccharomyces cerevisiae is Brewer’s or Baker’s yeast. Crohn’s patients have high prevalence of abnormal antibodies 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. Some people with positive ASCA do not have Crohn’s disease that can be confirmed by colonoscopy, capsule endoscopy, x-rays or intestinal biopsies. However, it may that these people have a “pre-Crohn’s” condition or very early Crohn’s disease. In my experience, these individuals often have symptoms that improve when treated with medications and probiotics as if they had Crohn’s disease.
OmpC is the abbreviation for an antibody that is present in many Crohn’s patients. The antibody is to the outer membrane porin protein of the bacteria E. coli though that bacterium is not thought to be the cause of Crohn’s disease.
Prometheus Laboratories added this antibody test to its IBD serologies in 2006 and named the complete panel of antibody tests IBD 7. The antibody is to a specific protein on a bacterium that constitutes the flagelin or hair like structure enabling movement and attachment of bacterium to the intestine. This protein is called CBir1 flagelin. When antibodies to this protein are high levels, especially when ASCA and/or OmpC are antibodies are also present, it is highly predictive of Crohn’s disease. When present at high levels along with a certain pANCA pattern, it is associated with Crohn’s colitis more commonly than ulcerative colitis. Though generally believed to be more specific for Crohn’s disease, antibody to CBir1 may present but not particularly elevated and associated UC pattern of pANCA when ulcerative colitis is present.
Yes, Prometheus Laboratories have identified specific patterns that include normal levels of these antibodies that are predictive of IBD. They have a proprietary computer algorithm that is used to analyze these protein patterns and offer a prediction regarding the presence of IBD.
The results to the left were from a patient with established Crohn's disease yet the Prometheus pattern was determined by the computer to not be predictive of Crohn's.