The role of quality of life in functional gastrointestinal disorders: regulatory issues.

Generic questionnaire such as SF36 and functional gastrointestinal disorder (FGD)-specific questionnaires (i.e. IBSQOL or FGDQL) are now available for the evaluation of new drugs for the treatment of irritable bowel syndrome or functional dyspepsia. For regulatory issues it is necessary to describe in detail the scale of the QOL questionnaire, its psychometric properties and reason for its choice, as well as validation studies, populations concerned, means of administration and methods for analysis. Preselection of few dimensions of the QOL questionnaire, if necessary, has to be explained. QOL results have to be compared with symptom scores. Trials have to be double-blind placebo- controlled studies with a sample size calculation taking account of the high placebo-response. No official guidelines are available in FGD and more validation studies are needed to help in the choice of the specific QOL questionnaire, in the metrologic analysis and in the interpretation of QOL changes during FGD treatment. Then QOL questionnaires could become a primary end point in clinical trials if efficient drugs for FGD treatment are developed.