Quality of life in functional dyspepsia: responsiveness of the Nepean Dyspepsia Index and development of a new 10-item short form

Background: The Nepean Dyspepsia Index is a reliable and valid measure of q uality of life in functional dyspepsia, but responsiveness has been little studied. The Nepean Dyspepsia Index originally contained 42 items designed to measure impairment of a subject's ability to engage in relevant aspects of their life because of dyspepsia, and their enjoyment of these aspects; i n addition, the individual importance of areas was assessed. It was subsequ ently shortened to 25 items, yielding five sub-scales. Aim: To test the Nepean Dyspepsia Index's responsiveness and develop a resp onsive, very short form. Methods: A randomized, double-blind controlled trial was performed in 589 p atients with documented functional dyspepsia. Symptoms and quality of life were measured at baseline, 2 and 4 weeks. Responsiveness of the Nepean Dysp epsia Index quality-of-life section was evaluated by correlation with sympt om scores and calculation of standardized changes in scores. Two items from each sub-scale which best represented the area of life (by factor loadings ) were selected to create the 10-item short form (SF; short form-Nepean Dys pepsia Index). Internal consistency was assessed by Cronbach's alpha and re sponsiveness was assessed as above. Results: The Nepean Dyspepsia Index quality-of-life scales demonstrated exc ellent responsiveness to change in both the active and placebo arms (standa rdized response means all > 1.0). The Nepean Dyspepsia Index accounted for only 8% of the variance in percentage change in symptoms (by visual analogu e scales), indicating that it was evaluating areas of life not covered by s ymptoms. The 10-item short form had adequate internal consistency (all scal es greater than or equal to 0.70) and all strongly (and significantly) corr elated with the long form sub-scales; it was also highly responsive. Conclusion: The Nepean Dyspepsia Index is a responsive disease-specific qua lity-of-life measure; the 10-item short form can be applied in clinical tri als of functional dyspepsia.