Prevalence, investigational pathways and diagnostic outcomes in differing irritable bowel syndrome subtypes

There has been increasing interest in subclassifying irritable bowel syndrome (IBS) to make a positive diagnosis.

The aim of this study was to assess the population prevalence of differing subtypes, investigational pathways and diagnostic outcomes.

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.

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).

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.