Questionnaires for measuring quality of life in patients with inflammatory bowel disease usually include a large number of items and are time-consuming for both administration and interpretation. Our aim was to elaborate and validate a short quality-of-life questionnaire with the most representative items from the Spanish version of the 36-item Inflammatory Bowel Disease Questionnaire (IBDQ-36) using the Rasch analysis. The responses to 311 IBDQ-36 questionnaires from 167 patients with ulcerative colitis (UC) and 144 with Crohn's disease (CD) were analyzed.
IBDQ-36 was shortened with successive Rasch analyses until all the remaining items showed acceptable separation and goodness-of-fit properties. Validation of the short questionnaire was studied in a new group of 125 patients by determining its validity and reliability.
A 9-item short questionnaire was obtained (IBDQ-9). Its correlation with IBDQ-36 was excellent (r = 0.91). Correlation between IBDQ-9 and clinical indices of activity was statistically significant in UC (r = 0.70) and CD (r = 0.70). IBDQ-9 score discriminates adequately between patients in clinical remission or relapse (P < 0.01). Sensitivity to change was determined in 14 patients who improved clinically, showing significant IBDQ-9 changes between both determinations (P < 0.01), with an effect size of −2.67 in UC and −5.29 in CD. IBDQ-9 was also homogeneous, with a Cronbach's α of 0.95 in UC and 0.91 in CD. In 35-clinically stable patients, test-retest reliability was good, with a statistically-significant correlation between both questionnaires (r = 0.76 in UC and 0.86 in CD, P < 0.01) and an intraclass correlation coefficient of 0.82 in UC and 0.84 in CD.
In conclusion, a short and valid questionnaire to measure quality of life in patients with inflammatory bowel disease was obtained using a new measurement model. Its use should facilitate comprehension of the impact of inflammatory bowel disease.