Impact of irritable bowel syndrome on patients' lives: development and psychometric documentation of a disease-specific measure for use in clinical trials.
OBJECTIVE
To develop a disease-specific questionnaire to capture the impact of irritable bowel syndrome (IBS) and its treatment on patients' lives, the Irritable Bowel Syndrome Impact Scale (IBS-IS).


METHODS
One hundred and fifty-five IBS patients participated (126 (81%) female; age (mean+/-SD) 45.5+/-12.4 years). We developed the initial 39 items from the literature, available IBS-specific instruments and input from physicians, nurses and patients. We deleted IBS-IS items with a high ceiling effect, items that measured a different construct and items showing a high correlation (r>0.90) with another item and with Rasch analysis, leaving 26 items. We then applied exploratory factor analysis to examine domain groupings. Subjects completed the IBS-IS instrument, the Gastrointestinal Symptom Rating Scale for IBS (GSRS-IBS), Short Form-36 (SF-36), Visceral Sensitivity Index (VSI), and Hospital Anxiety and Depression (HAD) scale. Internal consistency, construct validity and discriminate validity were assessed.


RESULTS
The 26 items represented five domains: fatigue, impact on daily activities, sleep disturbance, emotional distress and eating habits. The internal consistency reliability for the domains was 0.87 to 0.96. Most associations between similar constructs in the IBS-IS, GSRS-IBS, SF-36, VSI, and HAD were >0.40. Each IBS-IS domain score decreased with increasing IBS symptom severity (P<0.05), and the patients scored >5 score units lower than a US general population scored on all eight SF-36 dimensions.


CONCLUSIONS
The IBS-IS is a short, user-friendly instrument with excellent psychometric properties that has potential usefulness for clinical trials.
Longstreth
George F
GF
Department of Gastroenterology, Kaiser Permanente Medical Center, San Diego, California, USA. George.F.Longstreth@kp.org
Bolus
Roger
R
Naliboff
Bruce
B
Chang
Lin
L
Kulich
Károly R
KR
Carlsson
Jonas
J
Mayer
Emeran A
EA
Naesdal
Jörgen
J
Wiklund
Ingela K
IK
D000203:Activities of Daily Living; D000328:Adult; D004644:Emotions; D005221:Fatigue / Q000209:etiology; D005247:Feeding Behavior; D005260:Female; D006801:Humans; D043183:Irritable Bowel Syndrome / Q000150:complications / Q000523:psychology*; D008297:Male; D008875:Middle Aged; D011594:Psychometrics; D011788:Quality of Life; D012680:Sensitivity and Specificity; D018434:Sickness Impact Profile; D012893:Sleep Wake Disorders / Q000209:etiology