Ultrasound remission after biologic induction and long-term endoscopic remission in Crohn's disease: a prospective cohort study

Background: The Bowel Ultrasound Score (BUSS) accurately detects therapy-related changes by using the Simple Endoscopic Score for Crohn's disease (SES-CD) as the reference standard. We aimed to evaluate ultrasound remission as a treatment target and its prediction for long-term endoscopic remission.

Methods: This single-centre prospective observational study, based at a tertiary referral centre in Milan, Italy, enrolled, between March 1, 2018, and January 31, 2021, adult patients with active CD (SES-CD >2) who were starting biologics. Colonoscopy and IUS was performed at baseline and at 12 months (mean 12.8 ± 4.2). The primary outcome was the predictive value of ultrasound remission at week 12 (BUSS ≤3.52) for long-term endoscopic remission at 12 months. The International Bowel Ultrasound Segmental Activity Score (IBUS-SAS) was also calculated and optimal cut-point to detect endoscopic remission was identified through ROC analysis.

Findings: 93 patients with CD were included. Of these, 22 patients (24%) achieved endoscopic remission. Week 12 ultrasound remission predicted endoscopic remission (59% compared with 41% of the patients who were not in ultrasound remission; OR 9.93, 95% CI 3.10-31.80; p < 0.001), while week 12 calprotectin values (<50, <100, <250 μg/g) did not. Week 12 ultrasound activity was associated with failure to achieve long-term endoscopic remission (NPV 87%, PPV 54%). IBUS-SAS cut-off to discriminate endoscopic remission was 22.8 (AUC 0.906). ROC curve comparison showed no-significant difference between BUSS and IBUS-SAS (p = 0.46) for detecting endoscopic remission.

Interpretation: Early ultrasound remission predicts long-term endoscopic remission, making it a valuable early treatment target for clinical practice and in clinical trials. Larger multicentre validation studies are warranted to confirm these findings.

Funding: None.