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IBS can be difficult to diagnose. IBS is called a diagnosis of exclusion, which means a doctor considers many other alternatives first, performing tests to rule out other medical problems. Some of these tests may include laboratory studies, imaging studies (such as a CT scan or small intestinal X-rays), and endoscopy and/or colonoscopy). An endoscopy is a procedure in which a flexible tube with a tiny camera at one end is passed into the GI tract while the patient is under conscious sedation. A combination of history, physical examination, and selected tests are used to help diagnose irritable bowel syndrome.
Two relatively new blood antibody blood tests may help doctors and other medical specialists diagnose irritable bowel syndrome with diarrhea or IBS-D, and irritable bowel syndrome mixed or IBS-M (irritable bowel syndrome with constipation and diarrhea).
These new blood tests are for anti-CdtB and anti-vinculin antibodies, which researchers believe, are thought to develop in some patients after having had acute) acute gastroenteritis caused by several different, common types of bacteria. The overgrowth of these bacteria in the gut may trigger an immune attack on the patients’ own intestinal tissues (autoimmunity) with the ensuing inflammation and damage to the tissues, which causes IBS symptoms.
The test appears to be of use in diagnosing patients with irritable bowel syndrome with diarrhea IBS-D, but not IBS with constipation (IBS-C). The tests appear to be specific, and if the antibodies are present, it is highly likely that the patient has IBS. However, the tests are insensitive, which means that if the antibodies are not present, the patient still may have IBS. Thus, the tests may be identifying only a subset of individuals with IBS, those with post-infectious IBS. The FDA has not approved irritable bowel syndrome, nor have they undergone rigorous scientific examination for effectiveness. The test expected to cost from $500 to over $1,000.