Subtypes of Irritable Bowel Syndrome Based on Abdominal Pain/Discomfort Severity and Bowel Pattern

Irritable bowel syndrome (IBS) has traditionally been classified by stooling pattern (e.g., diarrhea-predominant). However, other patterns of symptoms have long been recognized, e.g., pain severity. Our objective was to examine the utility of subtyping women with IBS based on pain/discomfort severity as well as predominant bowel pattern. Women (n = 166) with IBS completed interviews, questionnaires, and kept a diary for 28 days. Rome II questionnaire items eliciting the past year recall of hard and loose stools, and frequency and severity of abdominal pain or discomfort were used to classify participants into six subtypes-three bowel pattern categories by two pain/discomfort severity categories. Concordance of these subtypes with corresponding diary items was examined. Analysis of variance (ANOVA) tested the relationship of bowel pattern and pain categories to measures of quality of life and symptoms. There is moderate congruence of the retrospective classification of bowel pattern and pain/discomfort severity subtypes with prospectively reported stool frequency and consistency and pain severity. Quality of life, impact of IBS on work and daily activities, and cognitive beliefs about IBS differed significantly based on abdominal pain/discomfort category but not on predominant bowel pattern. There is evidence of an interaction, with the effect of pain severity being strong in the IBS-diarrhea and IBS-mixed groups, but this was absent in the IBS-constipation group. Similar results hold for most diary symptoms, except for those directly related to bowel pattern. Overall, the distress of IBS is more strongly related to the severity of abdominal pain/discomfort than is the predominant stool pattern in patients with IBS. Categorizing IBS patients by abdominal pain/discomfort severity in conjunction with predominant bowel pattern may be useful to clinicians and researchers in developing more effective management.