40 patients were prospectively examined with ultrasound and endoscopy in the development phase. The Simple Endoscopic Score for Crohn’s Disease (SES-CD) was used as reference standard. Seven ultrasound variables (bowel wall thickness, length, colour Doppler, stenosis, fistula, stratification and fatty wrapping) were initially included, and multiple linear regression was used to select the variables that should be included in the final score. Secondly, the ultrasound data from each patient were re-examined for interobserver assessment using weighted kappa and intra-class correlation. Finally, the activity index was validated in a new cohort of 124 patients.
Length, fistula and stenosis were excluded. The combination of the remaining variables provided a multiple correlation coefficient of r = 0.78. The interobserver analysis revealed poor agreement for stratification and fatty wrapping and these were thus excluded. There was excellent interobserver agreement for the remaining score consisting of wall thickness and colour Doppler. In both patient cohorts, the ultrasound score correlated well with SES-CD (Development cohort: rho = 0.83, p < 0.001, Validation cohort: rho = 0.78, p < 0.001). A ROC curve analysis revealed an area under the curve of 0.92 and 0.88 for detecting endoscopic activity and moderate endoscopic activity, respectively.
A simple ultrasound activity index for Crohn’s disease consisting of bowel wall thickness and colour Doppler was constructed and validated and correlated well with endoscopic disease activity.
© The Author(s) 2020. Published by Oxford University Press on behalf of European Crohn’s and Colitis Organisation.