Effect of Standardised Scoring Conventions on Inter-rater Reliability in the Endoscopic Evaluation of Crohn's Disease

The Crohn's Disease Endoscopic Index of Severity [CDEIS] and Simplified Endoscopic Score for Crohn's Disease [SES-CD] demonstrate consistent overall intra- and inter-rater reliability. However, the reliability of some index items is relatively poor. We evaluated scoring conventions to improve the reliability of these items.

Five gastroenterologists with no previous experience scoring the CDEIS or SES-CD were trained on their use. A total of 65 video recordings of colonoscopies were scored blindly by each gastroenterologist before and after additional training on index scoring conventions. Intra-class correlation coefficients [ICCs] assessed the effect of application of these conventions on the reliability of the CDEIS, SES-CD, and a Global Evaluation of Lesion Severity [GELS] score.

Following training on scoring conventions, inter-rater ICCs (95% confidence interval [CI]) for the total SES-CD score increased from 0.78 [0.71, 0.85] to 0.85 [0.79, 0.89]. The ICCs for the total CDEIS and GELS scores were not affected: corresponding inter-rater ICCs were 0.74 [0.65, 0.81] and 0.49, [0.38, 0.61] before and 0.73 [0.65, 0.81] and 0.53 [0.42, 0.64] following application of scoring conventions. Estimations of ulcer depth, surface area, anatomical location, and stenosis were important sources of variability.

Use of scoring conventions previously developed by expert central readers enhanced the reliability of the SES-CD but did not similarly affect the CDEIS or GELS. As the SES-CD is more likely to be reliable than the CDEIS and can be optimised with targeted training, it is the preferred instrument for use in clinical trials.