Validating Crohn's Disease Activity Indices for Use in Assessing Postoperative Recurrence

Background: The Crohn's Disease Activity Index (CDAI) has been used in medical trials with scores < 150 indicative of remission. Its value in assessing postoperative recurrence is unknown. The objective of this study was to explore the utility of the CDAI in determining the presence or absence of symptomatic disease recurrence in patients having previously undergone ileocolic resection for Crohn's disease. Methods: Ninety-three patients underwent clinical and colonoscopic evaluation within 12 months of ileocolic resection. Endoscopic appearance was assessed using the Rutgeerts score (i0-i4). Symptomatic disease recurrence was defined by the composite of symptom severity warranting therapy and an endoscopic score >= i2. CDAI scores were calculated. Comparisons were made using the receiver operator curve (ROC). Results: Thirty-nine (42%) patients had recurrent disease (22% symptomatic, 20% endoscopic only) at 12 months. Median CDAI for symptomatic recurrence was 198 (interquartile range [IQR]: 106-293), 80 for asymptomatic subjects (IQR 35-115). The area under the ROC curve for symptomatic disease and CDAI was 0.78 (95% confidence interval [CI] 0.64-0.91). Recurrence was best predicted by a CDAI of >= 148 (sensitivity 70%, specificity 81%). A strong linear relationship existed between the CDAI and Inflammatory Bowel Disease Questionnaire (r = 0.82). Conclusions: The CDAI performs reasonably well in the postoperative setting and 150 appears the best cutpoint for indicating symptomatic disease. However, it is likely not suitable for use as the primary outcome measure. These data suggest that a combination of symptom assessment plus endoscopic evidence of recurrence should remain the gold standard definition for assessing outcomes in postoperative CD trials.