Background: There has been increasing interest in subclassifying irritable bowel syndrome (IBS) to make a positive diagnosis.
Aim: The aim of this study was to assess the population prevalence of differing subtypes, investigational pathways and diagnostic outcomes.
Materials and methods: Data were prospectively collected from three groups between 2005 and 2012. Group 1 [n=1002, 55% female, mean age 39 years (range 16-93 years)] comprised healthy volunteers who were interviewed using the Rome III diagnostic questionnaire. In secondary care, group 2 [n=64, 80% female, mean age 44 years (range 23-79 years)] comprised patients with constipation-predominant IBS (IBS-C) and group 3 [n=333, 66% female, mean age 51 years (range 23-92 years)] comprised patients with diarrhoea-predominant IBS (IBS-D). In groups 2 and 3, demographic data and diagnostic yield of investigations were evaluated as per normal clinical practice.
Results: IBS prevalence in group 1 was 6% (60/1002). IBS-C patients were significantly older than those with IBS-D (mean age 45 vs. 30 years, P=0.027). In groups 2 and 3, patients with IBS-C underwent a total of 56 additional investigations (mean 0.88 per patient), which was significantly lower than the number of investigations undertaken in the IBS-D group of 734 (mean 2.2 per patient, P<0.001). Further investigations in group 3 (IBS-D) identified an alternative diagnosis in 22%, whereas in group 2 (IBS-C) this was 0% (P<0.0001).
Conclusion: This is the first study to evaluate the population prevalence of different IBS subtypes within a UK population. Although further investigations in IBS-D patients have led to alternative diagnoses, none were identified in the IBS-C population. The merits of investigating IBS-C patients should be questioned.