Abstract
BACKGROUND: Irritable bowel syndrome (IBS) is a common disorder characterised by recurrent abdominal pain and altered bowel habits. Although IBS is classified according to stool form, symptom patterns fluctuate over time, posing challenges for subtype-based management. AIMS: To assess stability of IBS classification over 12 months using four approaches: stool form, most troublesome symptom, a seven-cluster latent class analysis (LCA) incorporating gastrointestinal and psychological symptoms and a simplified LCA based on degree of psychological burden. METHODS: Participants were recruited from ContactME-IBS, a national UK registry. Individuals meeting Rome IV criteria for IBS completed validated online questionnaires at baseline and 12 months assessing gastrointestinal and psychological symptoms. Participants were sub grouped according to the four classification methods, and stability between baseline and follow-up was evaluated using Cohen's kappa statistic. RESULTS: Of 752 participants meeting Rome IV criteria at baseline, 352 completed 12-month follow-up, with 259 (73.6%) continuing to meet Rome IV criteria. The highest stability was observed for stool form-based subtyping (κ = 0.60), particularly in IBS with diarrhoea (83% remained stable). Classification based on psychological burden showed similar stability (κ = 0.54). In contrast, subgrouping by most troublesome symptom (κ = 0.47) and the seven-cluster LCA (κ = 0.37) demonstrated lower stability. CONCLUSION: Different IBS classifications showed only moderate stability over 12 months, highlighting the fluctuating nature of the disorder. Stool form and psychological burden-based systems were most stable, but no method fully captured IBS variability. Future work could develop dynamic models integrating gastrointestinal and psychological factors to better guide management.