Correlation of Ultrasound Scores with Endoscopic Activity in Crohn's Disease: A Prospective Exploratory Study

Background and aims: Intestinal ultrasound [IUS] is widely accepted as a reliable tool to monitor Crohn's disease [CD]. Several IUS scores have been proposed, but none has been formally accepted by international organizations. Our aim here was to compare the available scores regarding their correlation with endoscopic activity. Methods: Consenting CD patients undergoing ileocolonoscopy at our Unit between September 2021 and February 2023 were included. Endoscopic activity was defined as SES-CD ≥ 3 or Rutgeerts score ≥ i2b for operated patients. IUS was performed within 6 weeks of endoscopy and scored with IBUS-SAS, BUSS, Simple-US and SUS-CD scores. All correlations were performed using Spearman's rank coefficient [rho = ρ]. Receiver operating characteristic [ROC] curves were compared with the Hanley and McNeil method. Results: Of 73 CD patients, 45 [61.6%] presented endoscopic activity, of whom 22 were severe [30.1%]. All IUS scores showed a significant positive correlation with endoscopy [p < 0.0001], with IBUS-SAS ranking the highest [ρ = 0.87]. Similarly, IBUS-SAS was the most highly correlated with clinical activity [ρ = 0.58]. ROC analysis of IBUS-SAS for any endoscopic activity showed the highest area under the curve (0.95 [95% confidence interval 0.87-0.99]), with sensitivity of 82.2% and specificity of 100% for a cut-off value of 25.2. IBUS-SAS was statistically superior to all the other scores in detecting severe endoscopic activity [SES-CD ≥ 9 or Rutgeerts i4]. Conclusions: All IUS scores provided solid correlation with endoscopy and clinical symptoms. IBUS-SAS outperformed the others due to a more granular description that might help in stratifying different levels of disease activity. Therefore, the use of IBUS-SAS in centres with well-founded expertise in IUS can be suggested.