Small intestinal bacterial overgrowth may increase the likelihood of lactose and sorbitol but not fructose intolerance false positive diagnosis

Background. Small intestinal bacterial overgrowth (SIBO) is defined as a bacterial count of more than 105 colony-forming units per milliliter in duodenal aspirate. It shares many symptoms with carbohydrate intolerance, which makes the clinical distinction of the disorders difficult. The aim of the study was to examine the relationship between a positive carbohydrate breath test and the presence of SIBO suggested by a positive lactulose hydrogen breath test. Methods. The electronic database of the gastroenterology laboratory of a tertiary medical center was searched for all patients clinically tested for SIBO in 2012-2013 for whom previous results for lactose, fructose, and/or sorbitol breath test were available. The correlation between positive findings for carbohydrate intolerance and for SIBO was statistically analyzed. Results. The study group included 349 patients, 231 female and 118 male, of mean age 53±19 years. All had symptoms of abdominal bloating and gas. There was a statistically significant difference in rates of a positive breath test for lactose and sorbitol at ≤ 90 minutes between patients who were positive and negative for SIBO [χ²(1)=12.8, p < 0.01 and χ²(1)=9.5, p < 0.01 respectively]. Findings for fructose were not significant. There was no effect of age or gender. Conclusions. SIBO may represent an important reversible cause of carbohydrate intolerance. It may be especially prudent to exclude SIBO patients with an early peak (≤90 minutes) in H₂ excretion.