In this study we found strong agreement between self-administered and interview-based BFS scores. Even though use of validated questionnaires is the gold standard in research, our study shows that the BFS questionnaire can be a good option for assessment of bowel function in HD and ARM patients. Our findings support a recently published systematic review listing BFS as one of three recommended bowel function questionnaires for use in HD patients, and it is the preferred bowel function questionnaire of the OASIS-Holistic Care in Hirschsprung Disease Network Group [6, 11].

Question #3 recording frequency of defecation was the only question without perfect agreement between self-administered and interview-obtained answers. This question differs slightly from the others, as the answering options do not follow the same ordinal structure of four levels indicating increasing severity of problems as the rest of the questions. The clinical consultation revealed that some misunderstood the answering alternatives, not realizing that the first option was an interval. If the answers had been re-phrased to “less often than every other day,” “every other day to twice a day,” and “more often than twice a day” the question would probably have been easier to understand. However, this would break the structure in which the most favorable response always appears first. Therefore, a brief explanation or added note to question #3 is suggested.

Unclear markings are impossible to assign a definitive score without speaking directly to the patient. Unclear markings may be unintentional or because it is difficult to choose a single answer. When talking to the patients and parents, the latter seemed to be the most likely explanation. Symptoms and bowel function can fluctuate, and it may therefore be challenging to select one answer that accurately reflects the overall experience. Question #4, which concerns soiling, had the highest number of unclear markings. Together with question #5, it addresses both frequency and consequences of soiling and fecal accidents. This dual focus can make answering more difficult. For example, infrequent soiling does not necessarily mean that a change of underwear is never needed, just as daily soiling does not always require the use of protective aids. Some individuals may choose to use protection even when soiling episodes are rare, while others may not use protective aids even if they soil every day if the soiling is minimal.

We found that answers from the ARM group were corrected more often than those from the HD group. This was surprising since the questionnaire was originally developed to assess bowel function in ARM patients. We speculate that bowel function in ARM patients may be more irregular than in HD patients, which could make it harder for them to answer consistently. Since the BFS questionnaire was developed for ARM patients, it does not address obstructive bowel problems, a problem frequently occurring in HD patients. It is therefore possible that obstructive problems are missed when the BFS is used. It could also be that obstructive problems are reported as constipation and therefore are captured by question #6. Lastly, obstructive problems are often more pronounced in the first period after the pull-through and patients tend to overcome these problems as they get older. Most of the patients in this study had undergone pull-through many years ago and obstructive problems were therefore not prominent. Since severity of symptoms is graded by treatment intensity, adding botulinum toxin injections to grade 3 could make the response more precise for patients needing botulinum toxin injections, but not regular enemas.

In conclusion, we found strong agreement between self-administered and interview-based BFS scores. Our findings support the frequent use of the BFS questionnaire in HD and ARM research as it is a short questionnaire accurately describing bowel function.