Short CDAI: Development and validation of a shortened and simplified Crohn's disease activity index

Background: The aim of this study was to develop a shortened Crohn's Disease Activity Index (CDAI). Methods: A short CDAI was developed retrospectively using patient-level data from four budesonide clinical trials to select variables from the full CDAI which best predicted health-related quality of life as measured by the Inflammatory Bowel Disease Questionnaire (IBDQ), using the multiple linear regression model. The validity, reliability, and responsiveness of the short CDAI compared to the original CDAI were determined using data from nine clinical trials of budesonide. Results: The variables selected for the short CDAI were abdominal pain, diarrhea frequency, and general well-being. In all nine studies involving 1373 patients with active and inactive CD (5863 visits), the Pearson correlation coefficients between the short CDAI scores and the original CDAI scores at baseline (r = 0.899, P < 0.001), and the score differences (r = 0.963, P < 0.001) were excellent. The short CDAI accounted for 82.4% of the variance of the original CDAI. The intraclass correlation coefficient for the short CDAI was marginally better than that for the full CDAI, and both demonstrated good reliability (r = 0.600 versus r = 0.549). In patients with active CD who remitted during follow-up, the mean short CDAI scores decreased from 247 to 97, a score difference of 150 ± 60 points (P < 0.001). In patients with stable CD who relapsed, the mean short CDAI scores increased from 109 to 244 points, a score difference of 135 ± 62 points (P < 0.001). Conclusions: The short CDAI is a valid, reliable, and responsive tool for the measurement of CD activity.