Abstract
BACKGROUND: Hypomorphic variants of sucrase-isomaltase (SI) have been associated with irritable bowel syndrome (IBS) in adults, but how their presence influences therapeutic outcomes is uncertain. AIMS: To investigate the frequency of sucrase-isomaltase hypomorphic variants in patients with IBS and their association with short- and long-term outcomes after initiation of a FODMAP diet. METHODS: Clinical outcomes in patients with IBS were retrospectively examined at mean 7.1 (range 2.5-13.4) years after being educated on a FODMAP diet by a gastrointestinal dietitian and their current food intake (Comprehensive Nutrition Assessment Questionnaire) and gastrointestinal symptoms were documented at interview. DNA extracted from whole blood samples was analysed with the Illumina Global Screening Array for sucrase-isomaltase hypomorphic variants. RESULTS: Of 72 participants (62% female, median age 59 years), 54% had at least one hypomorphic variant of which 85% were single-carriers. On adjusted binary logistic regression analysis, no differences were noted across SI hypomorphic genotypic groups for retrospective analysis of initial response to a FODMAP diet or long-term symptom control. Current dietary intakes of sucrose or starch were not different between non-carriers and carriers, were directly related to FODMAP intake and did not differ in carriers according to adequacy of symptom control. Findings in those with diarrhoea-predominant IBS (n = 29) were similar to the those in the whole group. Too few double-carriers (n = 6) precluded the definition of associations. CONCLUSIONS: The presence of single sucrase-isomaltase hypomorphic variants is common but was not associated with short- or long-term outcomes or dietary intake for patients with IBS who were taught a FODMAP diet.