Development and Validation of the VAS-IBS

Items to be used in a questionnaire can be generated from the literature [14 ,15 ], and to get a conceptualization of the construct of interest a literature review of symptoms and inconveniences experienced by patients with IBS was performed. The most outstanding physical symptoms identified were divided into six main groups; Abdominal Pain, Diarrhoea, Constipation, Bloating and Flatulence, Abnormal bowel passage and Vomiting and Nausea. All symptoms except Vomiting and Nausea also support the diagnosis of IBS. Symptoms included in the group Abnormal bowel passage (straining, urgency or feeling of incomplete evacuation) might also be connected to diarrhoea, to constipation as well as to the use of laxatives [16 (link)] and these inconveniences have been reported by patients as minor problems [7 (link)]. Since it might be difficult to evaluate symptoms associated with Abnormal bowel passage on a scale, and the VAS-IBS should serve as a complement to the anamnesis, it may be preferable to discuss these symptoms. One item for each physical symptom was created; Abdominal Pain, Diarrhoea, Constipation, Bloating and Flatulence, and Vomiting and Nausea. An overall item concerning the patient's bowel symptoms was also included in the questionnaire, and the intension was to use it as a control item for psychometric testing. This item was supposed to be removed in the final version of the VAS-IBS.
Besides physical health problems, IBS also has a negative influence on a person's mental health [17 (link),18 (link)] as well as on his/hers daily life [19 (link),20 (link)], and therefore questions related to these subjects were added. However, the focus of the questionnaire should still be on the patient's physical symptoms. Totally three items were created. One item related to mental health and two items related to daily life to see which of them best corresponded to the intention of the questionnaire. It is a common approach to have a number of items addressing a single underlying characteristic, and to use only one, all-inclusive, self-administered, single, global and item-specific question of each concept may appear to be insufficient. However, a single question may well provide information on all aspects of a phenomenon, and a summary of an individual's perception [21 (link)].
The time window was set to during the previous week, since that is the same time window as for the Gastrointestinal Symptom Rating Scale (GSRS) and the Psychological General Well-Being Index (PGWB), which were chosen as comparable questionnaires to test the criterion validity of the VAS-IBS.