Positive response to the IBD-F scale was reflected by a
high response rate for postal questionnaire at 77%, with only
0.2–5.5% missing items. The highest missing values (from 3.6
to 5.5%) were observed for questions 3, 4, 9, 12, 13 and 14 in
Section 2, where the N/A option applied. It is possible that
some respondents instead of selecting N/A left the box
unchecked