What tests are appropriate to confirm irritable bowel syndrome and exclude other significant disease?
The medical evaluation of people with suspected irritable bowel syndrome (IBS) can be quite variable. It depends on symptom presentation, age, and overall health of the person as well as the health care practices of the physician.
Recent studies suggest that, in the absence of alarm signs, few tests (if any) are needed to be certain that no other diagnosis is present in those who report symptoms compatible with IBS. However, there are several situations where additional testing should be considered, particularly in people with mostly diarrhea or diarrhea mixed with constipation.
If you go to a doctor for IBS symptoms, are above the age of 50, and have not previously had a colon examination (such as a colonoscopy), you should receive one as a screening test for colon polyps and cancer – not specifically for IBS.
A colon examination may also be done for younger people, particularly if the “red flags” or the doctor’s judgment lead to the suspicion of other bowel diseases such as inflammatory bowel disease.
For those with mostly diarrhea, biopsies (small tissue samplings) can be taken during the procedure to determine if microscopic colitis or mild inflammation of the colon is present. These changes in the tissue can be seen under a microscope. Microscopic colitis can mimic symptoms of IBS (abdominal discomfort and diarrhea) but are treated differently than IBS.
Blood test for Celiac Disease
Celiac disease is a genetic condition of the small intestine that develops in persons intolerant to gluten (a common ingredient in many foods including most grain and cereal foods as well as many processed foods). It causes malabsorption of nutrients and food and results in symptoms similar to those seen in IBS.
If the blood test is positive, an endoscopy should be performed to examine and biopsy the small intestine to confirm the diagnosis.
More recently there is some evidence that people may have symptoms due to gluten sensitivity in the absence of having celiac disease. In these cases there is no specific test, except to see that reducing gluten in the diet leads to meaningful improvement. However, be cautious not to adopt unneeded dietary restrictions.
Lactose Breath Test
If dairy product intolerance remains a concern despite dietary changes, a lactose breath test can be performed to confirm the diagnosis of lactose intolerance.
Importantly, even if another diagnosis is made, it may exist along with a diagnosis of IBS. The physician will then need to decide which condition or conditions are to be treated and how.