Small intestine bacterial overgrowth breath test does not predict symptom severity in gut-brain interaction disorders: role of anxiety, depression and inflammatory biomarkers.

Background: the high prevalence of disorders of the gut-brain interaction (DGBI), the availability of breath tests for the diagnosis of small intestine bacterial overgrowth (SIBO) together with some confusion about the concept of SIBO have led to an increase in the number of SIBO diagnoses.

Objective: this study aimed to analyze factors associated with the severity of gastrointestinal symptoms in patients undergoing a SIBO breath test.

Methods: a cross-sectional observational study including 70 patients who underwent a SIBO test with lactitol and completed questionnaires including the ROME IV criteria for irritable bowel syndrome (IBS), the Irritable Bowel Syndrome Severity Score (IBSSS), and HAD anxiety and depression scales. Additionally, blood levels of histamine, citrulline, ghrelin, intestinal-fatty acid binding protein (I-FABP) and transient receptor potential cation channel subfamily V, member 1 (TRPV-1) were measured.

Results: the mean age of the cohort was 45 ± 16 years and 70 % were female. Abdominal pain and/or abdominal distension were present in 85 % of patients and 44 % met IBS Rome IV criteria. IBSSS total score correlated with age (-0.354, p < 0.001), HAD-A (0.391, p < 0.001) and HAD-D (0.409, p < 0.001) scores, and histamine levels (0.279, p = 0.019). Abdominal pain correlated with levels of histamine (0.320, p < 0.05; 0.282, p < 0.05) and ghrelin (0.252, p < 0.05, 0.347, p < 0.05), while abdominal distension correlated with I-FABP levels (0.314, p < 0.05). The SIBO test was positive in 75 % but did not correlate with symptom severity.

Conclusion: this study unveiled some factors associated with the severity of abdominal pain and distension such as age, auto-perceived anxiety and depression and some biomarkers but not the SIBO test result.