Background:
Sucrose malabsorption and small intestinal bacterial overgrowth (SIBO) both have symptoms that overlap with common functional gastrointestinal disorders (FGID). These common symptoms include abdominal pain/cramping, bloating, and diarrhea. Recent studies have shown that sucrose malabsorption is more common than previously thought in patients with FGID. Due to the considerable overlap of symptoms, this study aims to identify the prevalence of sucrose malabsorption in patients undergoing SIBO breath testing and assess if there are symptoms that predict sucrose malabsorption in patients with FGID.

Methods:
Patients undergoing SIBO breath testing were recruited from August 2020 to March 2022. Patients completed the Rome IV Questionnaire for lower FGI/bowel disorders, IBS-SSS, and PAGI-SYM questionnaires and were provided an at-home ¹³C-sucrose breath test (SBT) (Metabolic Solutions, Inc., Nashua, NH). Abnormal sucrose digestion was indicated when the 90-minute breath sample reading of exhaled ¹³CO₂ was <5.10% for females or <3.91% for males after ingestion of the 20g sucrose solution. The SIBO breath test was considered positive if there was a 20ppm rise in hydrogen within 90 minutes or a presence of >10ppm in methane at any point in the breath test after ingestion of 75g of glucose or 10g of lactulose. Chi-square tests and t-tests were performed to identify differences between SBT⁺/SIBO^-, SBT^-/SIBO⁺, and SBT^-/SIBO^- patients.

Results:
Of the 300 patients who completed SIBO breath testing and consented to the study, 140 (47%) returned the SBT. Of those 140 patients, 19% (27/140) were SIBO positive. Of the remaining 113 patients who were SIBO negative, 22% (25/113) were SBT positive, and 78% (88/113) were SBT negative (Figure 1). Among patients who were SIBO negative, there were no statistically significant differences in predominant symptoms or prevalence of Rome IV lower bowel diagnoses (IBS, functional constipation, or functional diarrhea) between SBT positive or negative patients. There were also no differences in bloating frequency, IBS-SSS, or PAGI-SYM scores between the two groups (Table 1).
When comparing SBT⁺/SIBO^- patients (n=24) to SBT^-/SIBO⁺ patients (n=23), SBT positive patients reported less abdominal pain (p=0.044). The remaining predominant symptoms, lower bowel diagnoses, bloating frequency, IBS-SSS, and PAGI-SYM scores were similar between the two groups.

Conclusion:
In this study, the prevalence of positive SBT in patients referred for SIBO breath testing was 22%. Our findings suggest that predominant symptoms do not predict sucrose malabsorption on SBT. Further studies need to be conducted to determine which patients should be tested for sucrose malabsorption.

Colin Wu

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