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The diagnosis of an inflammatory bowel disease is primarily made with non-laboratory tests, but laboratory testing is an important tool for ruling out other causes of diarrhoea, abdominal pain, and colitis. These causes can include viral or bacterial infections, parasites, medicines, abdominal or pelvic radiation, colon cancer, and a variety of other chronic conditions such as coeliac disease and cystic fibrosis.

Laboratory Tests
Tests that may be requested to exclude other causes of diarrhoea and inflammation include:

Tests that are not specific for IBD but may be done to detect and evaluate the inflammation and anaemia associated with IBD include:

There are several tests that are not widely used clinically but that may sometimes be requested to help differentiate between ulcerative colitis and Crohn’s disease. These tests are not sensitive or specific enough to diagnose either condition, but they may give the doctor additional information. They include:

  • pANCA (Perinuclear anti-neutrophil cytoplasmic antibody) which is found in 60% to70% of those with ulcerative colitis, but only about 5% to 20% of those with Crohn’s disease.
  • ASCA (Saccharomyces cerevisiae antibodies), IgG and IgA. ASCA IgG is found in 80% of Crohn’s patients and in about 20% of those with colitis. ASCA IgA is found in 35% of Crohn’s patients but in less than 1% of those with colitis.

Non-Laboratory Tests
These tests are used to help diagnose and monitor IBDs. They can be used to look for characteristic changes in the structure and tissues of the intestinal tract and to detect blockages. Care must be taken during an acute attack or flare-up of an IBD, however, as there is a slight chance of perforating the bowel during testing.

  • Barium meal and follow through: after swallowing barium contrast dye, abdominal X-rays picture the small intestine
  • Sigmoidoscopy: a slender tube is used to examine the last 2 feet of the colon
  • Colonoscopy: a slender tube is used to examine the entire colon; it includes a light and camera and can be used to take biopsies
  • Biopsy: tissue samples taken from the intestine are evaluated for inflammation and abnormal changes in cell structure. The only easily available biopsies are those that can be taken from the inner surface of the intestine and from superficial biopsies such as these it may not be possible to determine whether the cause is Crohn’s disease or ulcerative colitis.

Last Review Date: June 4, 2017