Predisposing factors for positive D-Xylose breath test for evaluation of small intestinal bacterial overgrowth: a retrospective study of 932 patients.

Aim: To investigate, in the largest cohort to date, patient characteristics and associated risk factors for developing small intestinal bacterial overgrowth (SIBO) using the D-Xylose breath test (XBT).

Methods: We performed a retrospective cross-sectional study to analyze patient characteristics who underwent the XBT for evaluation of SIBO. Diagnostic testing with the XBT was performed based on a clinical suspicion for SIBO in patients with symptoms of bloating, abdominal pain, abdominal distension, weight loss, diarrhea, and/or constipation. Consecutive electronic medical records of 932 patients who completed the XBT at the University of Florida between 2005 and 2009 were reviewed. A two-way Analysis of Variance (ANOVA) was used to test for several associations including age, gender, and body mass index (BMI) with a +XBT. A two-way ANOVA was also performed to control for the differences and interaction with age and between genders. A similar analysis was repeated for BMI. Associations between medical conditions and prior surgical histories were conducted using the Mantel-Haenszel method for 2 by 2 contingency tables, stratified for gender. Reported odds ratio estimates reflect the odds of the prevalence of a condition within the +XBT group to that of the -XBT group. P values of less than 0.05 (two-sided) were considered statistically significant.

Results: In the 932 consecutive eligible subjects studied, 513 had a positive XBT. A positive association was found between female gender and a positive XBT (P = 0.0025), and females with a positive test were, on average, greater than 5 years older than those with a negative test (P = 0.024). The mean BMI of positive XBT subjects was normal (24.5) and significantly lower than the subjects with a negative XBT (29.5) (P = 0.0050). A positive XBT was associated with gastroesophageal reflux disease (GERD) (OR = 1.35; 95%CI: 1.02-1.80, P = 0.04), peptic ulcer disease (PUD) (OR = 2.61; 95%CI: 1.48-4.59, P < 0.01), gastroparesis (GP) (OR = 2.04; 95%CI: 1.21-3.41, P < 0.01) and steroid use (OR = 1.35; 95%CI: 1.02-1.80, P = 0.01). Irritable bowel syndrome, independent proton-pump inhibitor (PPI) usage, or previous abdominal surgery was not significantly associated with a positive XBT. No single subdivision by gender or PPI use was associated with a significant difference in the odds ratios between any of the subsets.

Conclusion: Female gender, lower BMI, steroid use, PUD, GERD (independent of PPI use), and GP were more prevalent in patients with SIBO, determined by a positive XBT. Increasing age was associated with SIBO in females, but not in males.