Improved validation of the Inflammatory Bowel Disease Questionnaire and development of a short form in Greek patients.

Abstract

The Inflammatory Bowel Disease Questionnaire (IBDQ) is a disease-specific questionnaire for assessing health-related quality of life. The main objective of this study is to assess three main areas of the validation of the Greek IBDQ: internal validity, designating items to dimensions, and selecting items for a short form. An additional aim is to present alternative validation methods for improved and robust results. A total of 134 patients with IBD, including 74 with ulcerative colitis (UC) and 60 with Crohn's disease (CD), completed the Greek IBDQ. Internal validity was assessed by using standard methods and multiple correlation analysis. Factor analysis of the 32 items of the questionnaire was carried out to identify the underlying dimensions, using principal factor analysis and maximal likelihood. For selecting items for a short form, three methods of linear regression analysis were used. All items had adequate convergent validity (except item 11 in the CD group) and acceptable discriminant validity (except item 11 for both groups). Factor analysis yielded five factors (emotional function, social function, systemic symptoms, bowel symptoms, and abdominal symptoms). The combination of three regression techniques and their internal validity yielded two similar but distinct short forms, one for UC and one for CD. Both forms had high correlation with the total IBDQ score (R(2) = 0.949 and 0.977, respectively). The Greek IBDQ had good internal validity. The original designation in four dimensions and the original short form could be improved with only slight modifications.