Quality of life in persons with irritable bowel syndrome: development and validation of a new measure.

How irritable bowel syndrome (IBS) and its treatment affect quality of life (QOL) is important. To develop a quality-of-life measure specific to irritable bowel syndrome, items were generated using a conceptual model and qualitative interviews with persons diagnosed using the Rome criteria. Symptom frequency and bothersomeness indices were created. Psychometric evaluation methods involved an initial cross-sectional survey followed by a repeat survey. The resulting 34-item measure demonstrated high internal consistency (Cronbach's alpha = 0.95) and high reproducibility (ICC = 0.86) with average time of seven days (SD = 1). For discriminant validity: number of symptoms (P < 0.05), self-reported severity of symptoms (P < 0.001), and the functional bowel disorder severity index (P < 0.001) significantly predicted IBS-QOL scores. Convergent validity and analyses confirmed predictions that scores are more closely related to psychological well-being (0.45) than to function (0.36). We conclude this measure meets established psychometric criteria for reliability and validity; testing of its responsiveness is warranted.