Do Patients With Irritable Bowel Syndrome Exhale More Hydrogen Than Healthy Subjects in Fasting State?

TO THE EDITO R: Irritable bowel syndrome (IBS) is a common disorder characterized by persistent or recurrent abdominal pain and discomfort with altered bowel habits. It affects approximately 10%-20% of the adult population, with typical symptoms like abdominal pain, constipation, diarrhea and bloating. 1,2 Although IBS is not lethal, it can reduce quality of life and increase medical costs. While the cause of IBS is still unclear, visceral hy-persensitivity, immune activation, enteric neuromuscular dys-function and dysfunction of the brain-gut axis have been suggested. 3-6 Small intestinal bacterial overgrowth (SIBO) has also been proposed as an etiologic factor in IBS, but the evidence is conflicting yet. 7 With great interest, I read the report by Kumar et al 8 regarding the increased fasting breath hydrogen levels among patients with IBS as compared with healthy controls (HC). Kumar et al 8 suggested that average fasting breath hydrogen was higher in patients with IBS as compared to HC (mean 10.1 ± 6.5 vs 5.5 ± 6.2 ppm, p ＜ 0.001) and number of stools per week correlated with average fasting breath hydrogen excretion in patients with IBS (r = 0.26, p = 0.02). The fasting breath hydrogen level was not different between patients with diarrhea predominant IBS (D-IBS) and constipation predominant IBS (C-IBS) (either by subjective feeling or by Bristol Stool Form Scale). Although the authors showed a clear result of different fasting breath hydrogen levels between IBS and HC, some doubt was raised because it is inconsistent with the previous results of same study group. Breath hydrogen levels were similar between IBS excluding D-IBS and HC, whatever fasting or following glucose ingestion, and the breath hydrogen levels following glucose ingestion were higher in chronic non-specific diarrhea including D-IBS than other types of IBS and HC according to the previous report. 9 I wonder why the fasting breath hydrogen levels were not different between D-IBS and C-IBS in the present study. I think that the result might have changed if the authors classified the IBS subtypes by Rome III criteria. 10 I also wonder about the frequency of C-IBS subtype which was higher than D-IBS, when 77 of 81 IBS patients (95.1%) complained loose stool at the onset of pain. 8 In the previous studies, fasting breath hydrogen levels were not different among patients with IBS and controls, contrary to the result from the present study. 11-13 Even the breath hydrogen levels following …