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Lab tests predict response to diet in patients with irritable bowel syndrome.

Of 145 patients with diarrhea-predominant irritable bowel syndrome and normal small-bowel architecture (indicating that absence of celiac disease), 37% had elevated IgG antigliadin and/or tissue-transglutaminase antibodies, and 39% were positive for HLA-DQ2 (which is strongly associated with celiac disease). Forty-one of the 145 patients followed a gluten-free diet for six months. Diarrhea and other gastrointestinal symptoms resolved in 60% of the patients who were positive and in 12% of those who were negative for HLA-DQ2 and celiac disease-associated serum antibodies. Both parameters combined yielded positive and negative predictive values of 56% and 88%, respectively. Sensitivity was highest (92%) for the presence of HLA-DQ2. Specificity was highest (76%) for the combination of HLA-DQ2 and elevated IgG antigliadin and/or tissue-transglutaminase antibodies.

Comment: Previous studies have shown that gluten intolerance can occur in the absence of celiac disease. Symptoms that may result from gluten intolerance in non-celiac patients include aphthous ulcers, various neurological syndromes, and diarrhea or other gastrointestinal complaints. The results of the present study indicate that in a high proportion of patients with diarrhea-predominant irritable bowel syndrome, gluten intolerance is the main etiological factor. The study also showed that certain laboratory tests that are used to diagnose celiac disease can also predict which patients with diarrhea-predominant irritable bowel syndrome are most likely to respond to a gluten-free diet. However, since there were a number of false-positives and false-negatives associated with these tests, a therapeutic trial of a gluten-free diet is still the most reliable way to determine who is going to benefit. In my experience, patients who are going to improve on such a diet almost always see results in three weeks or less, so a longer-term elimination diet is rarely necessary. Wheat is by far the most common symptom-evoking gluten grain. Barley and rye are less likely to cause symptoms, and the vast majority of gluten-sensitive individuals seem to tolerate oats.

Wahnschaffe U, et al. Predictors of clinical response to gluten-free diet in patients diagnosed with diarrhea-predominant irritable bowel syndrome. Clin Gastroenterol Hepatol. 2007;5:844-850.

by Alan R. Gaby, MD

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Title Annotation:Literature Review & Commentary
Author:Gaby, Alan R.
Publication:Townsend Letter
Geographic Code:1USA
Date:Jan 1, 2008
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