The use of International Bowel Ultrasound Segmental Activity Score (IBUS-SAS) in patients with ulcerative colitis: applicability and comparison with other ultrasound scores

The International Bowel Ultrasound Segmental Activity Score (IBUS-SAS) is an intestinal ultrasound (IUS) score validated for Crohn's disease, potentially applicable to ulcerative colitis (UC). We aimed to confirm the applicability of IBUS-SAS to UC, while comparing its performance with other IUS scores. Adult patients with UC undergoing colonoscopy were prospectively included and scored with both the Mayo Endoscopic Subscore (MES) and the Ulcerative Colitis Endoscopic Index of Severity (UCEIS). IUS was performed within 4 weeks of endoscopy, measuring IBUS-SAS and other 5 UC-developed IUS scores. The Spearman's rank coefficient (ρ) was used to perform correlations, while receiver operating characteristic (ROC) curves were compared with the Hanley & McNeil method. In total, 185 patients were included. The IBUS-SAS showed a strong correlation with both the MES (ρ = 0.72, p < 0.01) and the UCEIS (ρ = 0.73, p < 0.01). Its AUC to detect an endoscopic activity of at least moderate severity (MES ≥ 2 and UCEIS ≥ 5) was 0.87 and 0.89, respectively. The optimal cut-offs of IBUS-SAS to detect a MES ≥ 2 and an UCEIS ≥ 5 were > 19 (sensitivity 79%, specificity 84%) and > 23 (sensitivity 88%, specificity 75%), respectively. Consistently, all the investigated IUS scores correlated with both the MES and the UCEIS (p < 0.01). The IBUS-SAS has an optimal performance in the assessment of UC endoscopic activity, despite having been initially developed for CD. Therefore, it might be adopted as reference score both for CD and UC activity.