The PRO instrument generally included baseline data, an assessment of bowel function, and the questionnaire was then subjected to the qualitative development and validation presented here (Fig. 2). The results of the content validation process are shown in a step-by-step overview in Additional file 1. The details of each step are presented below in the cognitive interviews and the pilot study.
The design of the instrument was decided in collaboration with patient representatives and healthy participants. The questions and answers in the Diet and Bowel Function Questionnaire (Section 3) were validated within this study
The validation process and subsequent revisions resulted in the final version of the Diet and Bowel Function Questionnaire presented below in Table 2. Questions and answers about background and bowel function that were also asked but not validated are shown in additional file 2 .
Version 1: Cognitive interviews
The common theme emerging from the focus group discussions [7] was “Diet strongly influences gut function in HD” and included the following three categories. The first category “A quest to regulate gut function through dietary strategies” derived from participants’ experiences of how and to what extent diet affects bowel function in children with HD and how participants used different food items to regulate bowel function. This category resulted in items 1–6 and item 13 regarding gut effects of specifically mentioned food items (Fig. 2). Commonly mentioned foods that affect bowel function, included in point 13, are fruits, vegetables, dairy products, dietary fiber, white bread, rice, pasta, fats, sweets and popcorn. Specific food-induced bowel symptoms that were mentioned in the focus group discussions were flatulence, pain, constipation and laxative effects, used as alternative responses in items 3 and 13.
The second category emerging from the focus groups was “Dietary restriction to control the impact of bowel function on family and daily life” including whether and to what extent food choices and food adjustments affected participants’ daily life and emotional state. Using the exact wording used by the parents, the second category covers items 7–11 (Fig. 2). Third category “I would like dietary and nutritional guidance to facilitate self-healing” refers to food-related gut literacy and forms point 12 (Fig. 2).
The first version of the PRO instrument was then validated through individual cognitive interviews with six participants: one clinical nutritionist, one 12-year-old healthy boy, and four parents (two mothers and two fathers) of healthy children: two boys and two girls, mean age 7 .5 (range 3–12) years. The interviews lasted 45-60 minutes each. According to the structure of the interview (comprehension and relevance, wording and overall assessment), participants reported that the items were generally easy to understand and of high importance. Regarding response options, distinguishing between options on a 5-point Likert scale was reported as difficult, as exemplified by one participant who said: “It’s hard to tell the difference between ‘Rarely’ and ‘Sometimes'”. As a result, the scale was converted to a 4-point Likert scale. Participants were also asked to have the option to answer in their own words in addition to the given alternatives. Therefore, the option “Please explain how” was added to 10 items.
Wording refinements were needed for all items, particularly for children’s understanding of the bowel function wording. The 12-year-old boy said: “Bowel function. I don’t know what that means, I’ve never heard that word before“. Considerable effort was made to understand key words such as “bowel function” which was changed to “stomach“, while ‘diet and eating habits’/ ‘different/specific types of food or drink’/ ‘dietary regimes’ were simplified to the terms ‘diet’ and ‘eating habits’. Portion size or regular/irregular meal times were reworked into the word “how you eat”. Initial complex wording in the item “If you/your child can avoid all types of food and drink that cause you/your child problems, how often do you think you will have stomach problems such as abdominal pain or bloating, or problems with bowel function such as constipation etc.?” was revised to: “Do you think it would be possible to avoid stomach or bowel problems by adjusting your diet?” (see Additional file 1 item 6 in PRO tool version 1). In addition, the formulation of food-related feelings was reported to be complex and required in-depth discussions. Therefore, item 10: “Does your/your child’s stomach or bowel problems affect you/your child psychologically?” was revised to: “Does your diet affect you emotionally?” (Additional file 1 ).
Evaluating the PRO instrument in its entirety, participants requested more detailed instructions on how to complete the questionnaire and how much involvement parents and, respectively, children should take in answering when answering together.
Version 2: Cognitive interviews
The second version of the PRO instrument was assessed through a second round of individual cognitive interviews with six other respondents: one 15-year-old boy with HD, one 15-year-old healthy boy, three parents (two fathers and one mother) of children with HD who are were three boys with a mean age of 5.3 (range 3–8) years and one parent of a healthy 6-year-old girl. The interviews lasted 30-45 minutes each. Assessing comprehensibility and relevance, the questions were reported to be both easy to understand and easy to answer, and of great importance to researching the role of diet on bowel function and daily life. Wording revisions were needed for 6/12 questions. In line with respondents’ requests, the question: “How often…?” was replaced by: “Do you…?” and the response option was changed from: “Never” to “No, never” (questions 3, 7 and 8). As a result of the difficulties in finding generally accepted expressions for emotions, the question: “Does your diet affect you emotionally?” was once again discussed extensively by all participants. Retaining the word “emotional,” it was reworded to: “Does your diet affect you emotionally?” (questions 10 and 11). One question was changed to be an active voice sentence: “Do you agree that your stomach is affected by different types of food?”; was changed to: “Do you agree that your diet affects your stomach? (eg constipation, diarrhea or bloating)”. For bowel effects: “Easier pooping” was replaced with: “Laxative effect” and “Constipation effect” (item 3).
The question, “Do you think it would be possible to avoid stomach or bowel problems by adjusting your diet?” was ultimately omitted as a result of the fact that one participant perceived it as offensive, signaling a lack of good parenting: “The issue puts pressure on you as a parent. If you haven’t had or heard of Hirschsprung’s disease, you’d think it was a diet-related disease. Instead, one question about the family’s eating habits was added, as dietary adaptations were asked to be defined within a family concept: “Does anyone else in your family adjust their diet to help their stomach?” ( point 6).
In the overall evaluation, several participants suggested that because food is chosen and prepared mostly by parents, the PRO instrument should be answered by both the child and the parent, regardless of the child’s age (below 18 years). The instructions were changed accordingly.
Version 3: Pilot test
The pilot test involved 10 healthy children (five girls and five boys) with a mean age of 7 years (range 2–15 years) and their parents. To emphasize the importance of answering question 13, as one respondent misinterpreted the instructions and therefore did not answer this question, an additional sheet was inserted between questions 12 and 13. To clarify between: “Do you choose certain types of food , to help your stomach? ” and: “Do you avoid certain types of food to help your stomach?” these two questions were changed from being paired in question 13 to separate single questions (questions 4 and 5). (Additional file 1). The question about dietary adjustments (question 3) was reworded from a main question: “If you adjust your diet because of your stomach, what are the reasons?” to: “Do you…” with a dichotomous yes/no response, with a follow-up question: If yes: why? After these revisions, the research team decided on the final version of the PRO instrument (Table 2). The Diet and Bowel Function Questionnaire, including baseline data and assessment of bowel function, can be found in an additional file (see Additional file 2 ).
The final version
The validation process described above and revisions to questions 1–13 regarding dietary effects on bowel function and daily life resulted in the final version of the Diet and Bowel Function Questionnaire, Table 2.