Diagnostic Utility of Carbohydrate Breath Tests for SIBO, Fructose, and Lactose Intolerance.

Unexplained bloating, gas, and pain are common symptoms. If routine tests are negative, such patients are often labeled as irritable bowel syndrome.To determine the diagnostic utility of breath tests that assess for small intestinal bacterial overgrowth (SIBO), fructose or lactose intolerance, and the predictive value of symptoms.

Patients with gas, bloating, diarrhea, abdominal pain (≥ 6 months), and negative endoscopy and radiology tests were assessed with symptom questionnaires, glucose (75 g), fructose (25 g), or lactose (25 g) breath tests. Breath tests were categorized as positive when H₂ (≥ 20 ppm) or CH₄ (≥ 15 ppm) increased above baseline values or as hypersensitive when symptoms changed significantly without rise in H₂/CH₄ or as negative.

1230 patients (females = 878) underwent 2236 breath tests. The prevalence of SIBO was 33% (294/883), fructose intolerance was 34% (262/763), and lactose intolerance was 44% (260/590). Hypersensitivity was found in 16% and 9%, respectively, during fructose and lactose breath tests. Although gas (89%), abdominal pain (82%), and bloating (82%) were highly prevalent, pretest symptoms or their severity did not predict an abnormal breath test, but symptoms during the breath test facilitated diagnosis of SIBO, fructose, and lactose intolerance and hypersensitivity.Approximately 45% of patients with unexplained gas and bloating had SIBO, fructose, or lactose intolerance; another 9-16% had visceral hypersensitivity. Pretest symptoms were poor predictors, but symptoms during the breath tests were useful. Breath tests are safe, provide significant diagnostic yield, and could be useful in routine gastroenterology practice.