Carbohydrate Malabsorption and Putative Carbohydrate-Specific Small Intestinal Bacterial Overgrowth: Prevalence and Diagnostic Overlap Observed in an Austrian Outpatient Center

Abstract

Background/Aims: While lactose malabsorption is a well-investigated condition, few epidemiologic data are available for fructose and sorbitol malabsorption. The aim of this study was to assess the prevalence rates for primary lactose malabsorption, fructose and sorbitol malabsorption, and carbohydrate-specific small intestinal bacterial overgrowth (cs-SIBO) in an Austrian outpatient center. Methods: In total, 306 adult patients, who were primarily referred with suspected carbohydrate malabsorption by general practitioners to our outpatient clinic, underwent genetic testing (C/T_-13910 polymorphism) for primary lactose malabsorption, and a combined hydrogen (H₂)/methane (CH₄) breath test for fructose (25 g) and sorbitol (12.5 g) malabsorption. Cohen's kappa (κ) was calculated for agreement between positive breath test results and self-reported symptoms during the test. Results: Seventy-eight (25.49%) patients were C/C_-13910 homozygotes, indicating primary lactose malabsorption. Thirty-four (11.11%) and 57 (18.63%) patients were classified as fructose and sorbitol malabsorbers. Cohen's κ measuring agreements between positive fructose and sorbitol breath test results and self-reported symptoms during the test were 0.33 and 0.49, respectively. Twenty-nine (9.50%) patients with an early H₂/CH₄ peak (i.e. within 60 minutes after fructose and/or sorbitol ingestion) were diagnosed with cs-SIBO. Conclusion: In Austria, carbohydrate malabsorption is a frequent condition in patients referred by general practitioners to carbohydrate malabsorption testing.