Introduction Small intestine bacterial overgrowth (SIBO) has been proposed as a cause of altered small bowel motility both in irritable bowel syndrome (IBS) and coeliac disease. The glucose hydrogen breath test (GHBT) is most commonly used in practice to diagnose SIBO. The aim of this study was to assess the prevalence of SIBO using GHBT in coeliac disease and IBS.
Methods Group A comprised patients with biopsy-proven, untreated coeliac disease (n=44, 14 male, median age 47 y, range 18–75). Group B comprised patients with IBS (n=207, 55 male, median age 53 y, range 17–90). Group C comprised controls (n=47, 9 male, median age 58 years, range 20–74). All had GHBT performed on a normal, gluten containing diet. In the coeliac group this was repeated after a median of 180 days on a gluten-free diet (GFD). None had antibiotics in the 4 weeks prior to testing. A positive result was a rise in hydrogen of at least 20 ppm, or methane of 12 ppm, over the baseline for each gas.
Results 6/44 (13.6%) with coeliac disease had a positive result. 30/207 (14.5%) patients with IBS had a positive breath test. 1/47 (2.1%) controls tested positive. Patients with coeliac disease (p=0.05) and IBS (p=0.02) were significantly more likely than controls to have a positive GHBT. In the coeliac group positive GHBT was associated with male sex but no other features. There were no associated features in groups B and C. Patients with coeliac disease had lower baseline hydrogen levels (9.4 ppm±8) compared with IBS patients (13.4 ppm±13.7) (p=0.07) and controls (16.6 ppm±18.0) (p=0.025). In the coeliac group 4/6 with a positive result had a significant rise in methane but not hydrogen. At repeat testing all four were persistently methane positive but the absolute peak methane levels had fallen from a mean of 64 ppm to a mean of 49 ppm. Only one coeliac subject had a positive GHBT that normalised on GFD.
Conclusion The prevalence of SIBO diagnosed by GHBT is similar in IBS and coeliac disease. SIBO is significantly more common in IBS and coeliac disease than in controls. The prevalence of SIBO in coeliac disease may not vary between treated and untreated disease. Despite this increased prevalence of SIBO in coeliac disease and IBS, the failure of prevalence to fall following GFD may suggest that neurodysmotility is not the method for symptoms in these patients.
Competing interests None declared.
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