Bowel ultrasound score is accurate in assessing response to therapy in patients with Crohn's disease

Background: We developed a non-invasive bowel ultrasound score (BUSS) to assess disease activity in Crohn's disease (CD). BUSS >3.52 is an indicator of endoscopic activity (SES-CD>2). Aim: To assess whether BUSS, in addition to detecting inflammatory lesions, also detects relevant changes of these lesions over time. Methods: This was a prospective observational study of 49 patients with active CD. All patients underwent bowel ultrasound and colonoscopy at baseline and at re-assessment after treatment with biologics and/or immunosuppressants. The primary objective was to assess the sensitivity to change of BUSS in patients treated for active CD, using the SES-CD as reference standard. Results: BUSS changed significantly from baseline to re-assessment in patients achieving endoscopic response (a reduction of SES-CD of at least 50% vs baseline: 4.87 [3.78-6.0] vs 2.47 [2.25-3.36], P < 0.001) and endoscopic remission (SES-CD <= 2: 4.65 [3.58-6.03] vs 2.25 [2.25-3.46], P = 0.003). A change of -1.2 in BUSS over time predicted endoscopic response (AUC 0.786, 95% CI 0.645-0.890; sensitivity 74%, specificity 83%). BUSS determined endoscopic response with 80% accuracy, and endoscopic remission with 78% accuracy. BUSS accurately detected changes in lesion severity (Guyatt score: 1.41 and standardized effect score: 1.74). BUSS did not change significantly in patients who did not achieve endoscopic response (5.62 [5.26-6.15] vs 5.70 [4.97-6.19], P = 0.53) or endoscopic remission (5.62 [5.18-6.14] vs 5.10 [4.58-6.05]; P = 0.10). Conclusion: BUSS is sensitive to change in CD.