Outcome measures in irritable bowel syndrome: comparison of psychometric and methodological characteristics

Although there is growing interest in irritable bowel syndrome (IBS) research, there is as yet no consensus regarding the preferred outcome measure. We aimed to evaluate and to compare the validity and appropriateness of available IBS outcome measures.

IBS symptom and IBS health-related quality of life (HRQOL) scales were identified through a literature search. In a panel evaluation, six reviewers independently rated the scales according to predetermined psychometric and methodological validation criteria.

Five IBS symptom scales and five IBS HRQOL instruments were identified. Two of the symptom scales were rated as good. The Adequate Relief question scored best. This scale demonstrates responsiveness as well as face and construct validity, and its score was considered easy to interpret and appropriate for use. According to the reviewers, the IBS Severity Scoring System performed well with regard to psychometric capacities, but its practical utility was considered debatable. The properties of the other three symptom scales were suboptimal. The practical utility of the five IBS-specific HRQOL scales was considered poor. However, the reviewers agreed that, at present, the IBS Quality of Life measurement (Patrick et al.) is the best choice, because it has been the most extensively validated and shows appropriate psychometric quality.

The Adequate Relief question is the measure of first choice when assessing global symptomatology as an outcome in IBS studies. For a more detailed IBS symptom assessment, the IBS Severity Scoring System is preferable. Finally, the IBS Quality of Life measurement scale can be used to establish changes in health-related quality of life.