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Chapter 2 40 Discussion This study demonstrates that 61.6% to 87.4% of Rome III IBS patients is likely to also fulfill the new Rome IV criteria for IBS, depending on the cut-off for abdominal pain severity used, when applying surrogate Rome IV criteria based on end-of-day symptom diaries. Regardless of the cut-off chosen, Rome IV-positive subjects were more often female, younger and recruited from secondary/tertiary care than Rome IV-negative subjects. Not only did they present with higher abdominal pain scores, but overall symptom severity was higher in Rome IV-positive subjects, including a higher percentage of visceral hypersensitivity as assessed by rectal barostat. Additionally, higher percentages of comorbid psychological symptoms and lower quality of life were found for Rome IV-positive subjects. Taken together, the current findings imply that the Rome IV IBS population will likely reflect a subgroup of Rome III IBS patients with more severe overall gastrointestinal symptomatology, psychological comorbidities and lower quality of life. To date, a recent study by Bai et al. investigated the agreement between Rome III and Rome IV criteria for IBS in a GI outpatient population in China. They found a moderate consistency between Rome III and Rome IV criteria, with prevalences of 12.4% and 6.1% based on Rome III and Rome IV criteria, respectively. 24 Similarly, Whitehead and colleagues reported prevalences of 10.7% and 5.7%, respectively, in a large population- based study. 8,9 Our current study confirms this decrease in prevalence by introducing Rome IV criteria, within a well-defined Rome III IBS population. Additionally, in line with these previously reported findings, our cut-off for abdominal pain severity of ≥3 may be most robust to define those subjects highly likely to fulfill Rome IV criteria, based on end-of-day diary. We observed that Rome IV-positive subjects were more often of female gender than Rome IV-negative subjects. These differences were not demonstrated by Bai and colleagues. 24 Differences in symptom severity between men and women, however, have been reported previously, indicating possible differences in pathophysiological mechanisms as well as in pain perception and coping strategies. A meta-analysis by Adeyemo and colleagues demonstrated that women are more likely to report abdominal pain than men. 25 Furthermore, higher overall IBS symptom severity in female IBS patients has been reported by Bjorkman et al . 26 These previous findings could explain the higher percentage of women in our Rome IV-positive IBS population compared to the Rome IV-negative subjects.