Abstract
BACKGROUND: Regulatory guidance for Crohn's disease trials recommends coprimary efficacy end points that evaluate both symptoms and mucosal inflammation. We aimed to characterize the operating properties of commonly used disease activity assessments alone and in combination. METHODS: Endoscopic and clinical data were available for 129 participants from the Study of Biologic and Immunomodulator Naïve Patients in Crohn's Disease trial. Readers scored the Simple Endoscopic Score for Crohn's Disease and the Crohn's Disease Endoscopic Index of Severity using standardized conventions. Index reliability was determined using intraclass correlation coefficients. Index responsiveness was assessed using standardized effect sizes based upon treatment assignment. Outcomes were evaluated for optimal sensitivity to treatment effect. RESULTS: Substantial inter-rater reliability was observed when the Simple Endoscopic Score for Crohn's Disease and Crohn's Disease Endoscopic Index of Severity were used as continuous measures (intraclass correlation coefficient, 0.64; 95% confidence interval [CI], 0.50-0.73; and 0.62 95% CI, 0.36-0.77) compared with moderate reliability when dichotomized (0.46; 95% CI, 0.26-0.65; and 0.51; 95% CI, 0.00-0.78). The Simple Endoscopic Score for Crohn's Disease, Crohn's Disease Endoscopic Index of Severity, patient-reported outcome-2, and Crohn's Disease Activity Index were similarly responsive (standardized effect size, 0.43, 95% CI, 0.05-0.81; 0.38, 95% CI, 0.0-0.76; 0.53, 95% CI, 0.15-0.91). A composite outcome of Crohn's Disease Activity Index score <150 and Crohn's Disease Endoscopic Index of Severity score <6 was most sensitive to treatment effect (28.9%; 95% CI, 11.0%-46.8%; P = .003). CONCLUSION: Endoscopic indices were more reliable as continuous measures. Composite outcomes including endoscopy improved sensitivity to treatment effect.