Diagnostic accuracy of the international bowel ultrasound segmental activity score for assessing disease activity in Crohn's disease.

BACKGROUND: Intestinal ultrasound (IUS) has emerged as a promising bedside tool for evaluating disease activity in Crohn's disease (CD), but real-world data using standardized ultrasound activity scores remain limited. METHODS: In this cross-sectional observational study, patients with ileal, colonic or ileocolonic CD underwent IUS and ileocolonoscopy within a two-week interval. IUS findings were quantified using the International Bowel Ultrasound Segmental Activity Score (IBUS-SAS). Endoscopic activity was assessed using the Simple Endoscopic Score for Crohn's Disease (SES-CD). Diagnostic performance of IBUS-SAS for detecting endoscopic activity (SES-CD ≥ 3) was evaluated using receiver operating characteristic (ROC) analysis. Construct validity was assessed using Spearman correlation, discordance analyses and multi-variable logistic regression. Segment-level correlations and diagnostic accuracy were also examined. RESULTS: Forty patients (median age 41 years; 18 [45%] female) with 160 bowel segments were analyzed. IBUS-SAS showed a moderate correlation with SES-CD (ρ = 0.45, p = 0.003) and FC (ρ = 0.35, p = 0.03. For detection of endoscopic activity, IBUS-SAS demonstrated an area under the ROC curve (AUC) of 0.75 (95% CI 0.52-0.97), numerically higher than FC, CRP and CDAI. At a cut-off of 24.0, IBUS-SAS achieved high sensitivity (96.7%) and negative predictive value (85.7%). Discordance analyses revealed progressively higher IBUS-SAS values with increasingly stringent composite definitions of disease activity. Segment-level analyses demonstrated stronger correlations and higher diagnostic accuracy in the transverse and left colon compared with the terminal ileum and ascending colon. CONCLUSIONS: The IBUS-SAS correlates with disease activity in CD and shows potential utility as a non-invasive rule-out and monitoring tool.