Predictors of response to a multidisciplinary internet-delivered intervention for irritable bowel syndrome: an explorative secondary analysis of a randomized controlled trial

Background Internet-delivered interventions for irritable bowel syndrome (IBS) have proven effective, but predictors of treatment response remain unclear. Aim To explore baseline patient characteristics and treatment-related variables associated with clinically meaningful improvement in IBS symptoms and quality of life following a multidisciplinary internet-delivered intervention. Methods This exploratory secondary analysis used data from a RCT ( n = 350) comparing internet-delivered cognitive behavioral therapy (CBT), FODMAP diet or their combination to patient education. Predictors were selected pragmatically based on clinical relevance and included demographic, clinical, psychological, dietary, and treatment-related variables related to outcomes. The primary outcome was defined as ≥ 50-point reduction on the IBS Severity Scoring System (IBS-SSS). In addition, two secondary outcomes were defined: 1) ≥ 30% reduction on the IBS-SSS and 2) ≥ 14-point increase on the Irritable Bowel Syndrome Quality of Life (IBS-QoL). Univariable and multivariable logistic regression models were used to explore the associations. Results More severe baseline IBS symptoms and higher baseline IBS-QoL were associated with increased odds of achieving ≥ 50-point reduction in IBS-SSS, whereas longer symptom duration and previous poor treatment effect of the FODMAP diet were associated with reduced odds of reduction. When treatment-related factors were added, adherence to patient education was associated with increased odds of reduction. For the secondary outcomes, the multivariable models including treatment‑related factors indicated that previous poor treatment effect of the FODMAP diet was associated with reduced odds of achieving a ≥ 30% reduction in IBS-SSS, whereas higher baseline IBS-QoL was associated with reduced odds of increased IBS-QoL. Across all outcomes, the explained variance of the models was low to modest. Conclusions No robust or consistent predictors of clinically meaningful improvement in IBS symptoms or quality of life were identified. Prior poor response to the FODMAP diet was associated with reduced odds of improvement across both responder definitions for IBS symptoms, suggesting that previous treatment experiences may be relevant to consider. Overall, these results highlight the limited utility of the assessed variables for forecasting individual treatment response and underscore the need for future research to identify more robust predictors and explore mechanisms of change in internet-delivered interventions for patients with IBS. Trial registration ClinicalTrials.gov ID NCT06117865. Registered 31.10.2023.