Supplementary Material for: High Prevalence of Small Intestinal Bacterial Overgrowth among Functional Dyspepsia Patients

<b><i>Background:</i></b> Small intestinal bacterial overgrowth (SIBO), characterized by either increased numbers or presence of colonic type bacteria in the small bowel has been previously described in functional dyspepsia (FD), based on breath testing. In this study, we aim to examine the prevalence of SIBO among FD patients using small bowel aspirate culture. <b><i>Methods:</i></b> We prospectively enrolled outpatients fulfilling Rome IV criteria for FD. Severity of symptoms was graded using the patient assessment of upper gastrointestinal symptom severity index (PAGI-SYM) questionnaire. Patients underwent upper gastrointestinal endoscopy and duodenal fluid was aspirated in sterile traps. SIBO was defined as ≥10³ colony forming units/mL of duodenal aspirate and/or presence of colonic type bacteria. Patients undergoing gastroscopy due to gastroesophageal reflux symptoms – control group (CG) – and patients with irritable bowel syndrome (IBS) fulfilling Rome IV criteria were also recruited. <b><i>Results:</i></b> We enrolled 227 FD subjects, 30 CG, and 90 IBS patients. Among FD patients, 144 (63.4%), 64 (28.2%), and 19 (8.4%) had postprandial distress syndrome (PDS), epigastric pain syndrome (EPS), and overlapping PDS-EPS syndrome, respectively. SIBO prevalence was 20.8%, 12.5%, and 31.6% among PDS, EPS, and overlapping PDS-EPS FD subtypes, respectively. Overall, SIBO prevalence was significantly higher in FD (44/227 [19.4%]) compared to CG (1/30 [3.3%]) (<i>p</i> = 0.037) and similar to IBS (44/227 [19.4%] vs. 15/90 [16.7%], <i>p</i> = 0.63) subjects. SIBO presence was associated neither with total nor with any subscale score of the PAGI-SYM questionnaire. <b><i>Conclusion:</i></b> In a cohort of Greek FD patients, SIBO prevalence was similar to that of IBS subjects and higher compared to that of controls.