Article Text


Small bowel I
PTU-154 Investigation of the optimal duration of the glucose hydrogen methane breath test
  1. E Grace1,2,
  2. K Thomas3,
  3. S Gupta3,
  4. A Lalji2,
  5. K Whelan1,
  6. C Shaw4,
  7. J Andreyev2
  1. 1Nutritional Sciences, King's College London, London, UK
  2. 2GI Unit, London, UK
  3. 3Research Data Management & Statistics Unit, London, UK
  4. 4Dietetics Department, The Royal Marsden NHS Foundation Trust, London, UK


Introduction Historically, the glucose hydrogen breath test has been popular for diagnosing small intestinal bacterial overgrowth (SIBO). Lately the glucose hydrogen methane breath test has become available. It is non-invasive and simple to carry out. This test is used as a part of standard clinical practice in patients suspected of having SIBO in our hospital. There are limited published data on the optimal test duration, with 3 h being the longest reported. This study aimed to determine if there is a significant difference in the number of patients who would be considered positive for SIBO depending on test duration.

Methods Patients in whom the gastroenterologist suspected SIBO underwent a breath test performed by endoscopy nurses using the QuinTron BreathTracker DP Digitial Microlyzer that measures hydrogen (H2) and methane (CH4) concentrations in parts per million (ppm). Pre-test preparation included avoiding slowly absorbed carbohydrates, fibre and large meals and limiting dairy intake and carbonated drinks for 24 h, a 12 h fast and avoiding exercise and cigarette smoking for 2 h. Breath H2 and CH4 concentrations were noted at baseline. Subjects then consumed 75 g (or 50 g if weight was <50 kg) in 100 ml of water. Thereafter, breath H2 and CH4 values were recorded every 20 min for 3 h (or less if positive). Positive test was defined as fasting H2 ≥20 or CH4 ≥10 ppm or a rise in H2 ≥12 or CH4 ≥6 ppm.

Results 98 males and 95 females, median age 63 years (range 28–86) underwent a breath test. Of these, 67 (35%) had a positive result for one or both gases: 18 (32%) at baseline, 39 (60%) by 40 min, 56 (84%) by 100 min, 60 (90%) by 140 min, 67 (100%) by 160 min. 126 patients had negative breath tests; n=75 had the test performed for a full 3 h, 26 (20%) had the test performed for 100 min only. In patients where the test was performed for 3 h the 95% CI for a false negative result at 100 min is 0.003 to 0.10.

Conclusion Most patients with SIBO will have a positive result by 100 min. This suggests that a reduction in the duration of the test can be achieved without compromising the number of true positives being diagnosed with SIBO.

Competing interests None declared.

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