Symptoms of irritable bowel syndrome in patients with inflammatory bowel disease: examining the role of sub-clinical inflammation and the impact on clinical assessment of disease activity

Background Symptoms compatible with irritable bowel syndrome (IBS) are frequently present in patients with inflammatory bowel disease (IBD); however, the cause of this phenomenon is unclear. Aim To determine the different contributions of true IBS' and sub-clinical inflammation in producing IBS-type symptoms in IBD patients, and to ascertain the impact these symptoms have on the clinical assessment of IBD activity. Methods In this cross-sectional study, 169 IBD patients completed questionnaires to assess disease activity, presence of IBS-type symptoms, and levels of anxiety and depression. Stool samples were collected for analysis of faecal calprotectin (FC). Results IBS-type symptoms were significantly more common in female patients (OR=4.64, 1.55-13.88) and were associated with higher levels of anxiety (OR=1.11, 1.01-1.21). There was no statistical difference between the FC levels of patients in clinical remission with IBS-type symptoms compared with those without (median values=111g/g vs. 45.5g/g respectively, P=0.171). The prevalence of IBS-type symptoms in patients with a normal FC level was 31%. Conclusions A substantial number of IBD patients with normal faecal calprotectin level experience IBS-type symptoms. These patients exhibit similar features to people diagnosed with IBS in the general community, suggesting that the conditions are not mutually exclusive and may coexist in a considerable number of IBD patients. A systematic diagnostic approach is required to assess IBD patients with IBS-type symptoms as sub-clinical inflammation may play a role in a proportion of cases.