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Rome III versus Rome IV criteria for IBS 41 2 With regards to clinical differences between Rome III and Rome IV IBS subjects, Bai et al. reported higher abdominal pain scores for Rome IV, but no differences in abdominal discomfort, abdominal bloating or demographic characteristics. In contrast, our study shows significantly higher scores for abdominal discomfort, bloating, flatulence, diarrhea and constipation, apart from abdominal pain. A possible explanation for the discrepancy between these studies is the method of data collection. Bai and colleagues retrospectively assessed the presence of above-mentioned symptoms at one time point, whereas in our study symptom severity scores were determined daily, using an end-of- day diary during 14 days. As a study by Engsbro et al. demonstrated that IBS subtype classification differs depending on whether retrospective ( i.e. Rome Diagnostic Questionnaire) or prospective methods ( i.e. diary cards) are used 27 , we did not use the symptom diary to asses the IBS subtypes. However, we feel that the end-of-day diary provides an objective overview of present symptoms during a 14-day period and therefore can be used to identify patients highly likely to fulfill the Rome IV criteria. Furthermore, Rome IV criteria require abdominal pain to be present at least once a week on average during the last three months. The end-of-day symptom diary as used only provides us with information about the past two weeks. However, all subjects fulfilled Rome III criteria assessed using the Rome III Diagnostic Questionnaire, which also requires the abdominal complaints to be present during the previous three months. Therefore, we think that the surrogate Rome IV criteria are a reliable reflection of the Rome IV Diagnostic Questionnaire. This is the first study focusing on clinical differences between Rome III and Rome IV IBS subjects. In conclusion, the current study underlines a decrease of IBS prevalence when using (surrogate) Rome IV compared to Rome III criteria. In addition to these findings, the question arises how to deal with the Rome IV-negative patient population presenting with IBS-symptoms in both primary and secondary/tertiary care and with regard to future clinical and mechanistic studies. First, it might be interesting to explore whether alternative Rome IV disorders can now be diagnosed in these subjects, for example functional constipation, functional diarrhea or functional abdominal bloating/distension. An exploratory analysis in the current study demonstrates that 24% is likely to fulfill Rome IV-criteria for FC, 34% for FD and 26% for FAB/D. These results should, however, be interpreted with caution, since these diagnoses are based on surrogate criteria, using an IBS-specific end-of-day symptom diary. Nevertheless, this suggests that an additional r 16% of Rome III IBS patients will