P-057 Reliability of Central Readers in the Evaluation of Endoscopic Disease Activity in Crohn’s Disease

Abstract

Endoscopic assessment of the mucosa is an evolving outcome measure in clinical trials in Crohn’s disease (CD). The Crohn’s Disease Endoscopic Index of Severity (CDEIS) and the Simple Endoscopic Score for Crohn’s Disease (SES-CD) are commonly used to evaluate endoscopic disease activity in clinical trials. However, neither instrument has been fully validated, and intra- or inter- rater reliability has only been studied on a limited scale. Four central readers (GD, PR, JWD, MD) reviewed video recordings of colonoscopies obtained from 50 patients with CD. Videos were captured using a standardized system, and evaluated, in random order, 3 times by each reader. Inter and intra-rater reliability for both instruments was assessed by calculating inter-class correlation coefficients (ICCs) and 95% confidence intervals (CI). Interpretation of ICCs was pre-defined based on the Landis and Koch benchmarks whereby a negative value reflects “poor” reliability, 0 to 0.2 “slight,” 0.21 to 0.40 “fair,” 0.41 to 0.60 “moderate,” 0.61 to 0.8 “substantial,” and above 0.81 “almost perfect” reliability.1 To assess validity, the CDEIS and SES-CD scores were also correlated with a global assessment of disease severity based on a 100 mm visual analog scale (VAS). Intra-observer intra-class correlation coefficients (ICCs) for the CDEIS, SES-CD and VAS scores (95% CIs) were 0.89 (0.86–0.93), 0.91 (0.87–0.94), and 0.81 (0.75–0.86), respectively. The corresponding inter-rater ICCs were 0.71 (0.61–0.79), 0.83 (0.75–0.89), and 0.62 (0.52–0.73), respectively. The correlation coefficient between the CDEIS and VAS is 0.75, the correlation between the SES-CD and VAS was 0.74, and the correlation between the CDEIS and SES-CD was 0.92. Central reading of endoscopic indices to assess CD severity, by a group of 4 experienced readers, had “substantial” to “almost perfect” intra- and inter- observer reliability. These results indicate that central reading is highly reliable for the assessment of CD endoscopic disease activity, and favor the value of the SES-CD. The substantial correlation observed between the endoscopic indices and the VAS- based global rating of disease activity supports their validity. Further study is needed to assess the responsiveness of endoscopic indices and to determine the optimum instrument for use in CD clinical trials. 1 Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977; 33:159–174.