Comparing Diagnostic Accuracy of High-end Intestinal Ultrasound Versus Mid-end Ultrasound With Tandem Ileo-colonoscopy in Inflammatory Bowel Disease : a Paired, Validating Confirmatory Study

The HUMID Study (High-end versus Mid-end Ultrasound in Inflammatory Bowel Disease Diagnostics) is a prospective, cross-sectional, paired diagnostic accuracy study designed to compare the performance of two intestinal ultrasound systems-a high-end system (Samsung RS85) and a mid-end system (Siemens ACUSON S2000)-in detecting ileocolonic inflammation in patients with inflammatory bowel disease. The study uses ileo-colonoscopy as the diagnostic reference standard and also evaluates the impact of ultrasound findings on clinical management and potential cost savings in resource-limited settings.

Eligible patients with known inflammatory bowel disease involving the colon and/or terminal ileum will undergo two intestinal ultrasound examinations followed by ileo-colonoscopy. To minimize operator bias, the mid-end ultrasound examination will be performed and interpreted by an experienced gastrointestinal sonologist using the Siemens ACUSON S2000 system. The high-end ultrasound examination will be conducted independently by an inflammatory bowel disease specialist using the Samsung RS85 system. Both sonographers will be blinded to each other's findings and to colonoscopy results. The examinations will be conducted in close succession on the same day, using standardized scanning protocols and probe frequencies suitable for bowel wall assessment.

Ultrasound assessments will include bowel wall thickness, mural stratification, vascularity, and disease extent. All findings will be recorded on pre-specified case report forms. Ileo-colonoscopy will be performed within 24 hours of the ultrasound exams by a separate blinded endoscopist. Endoscopic activity scores will be used as the reference standard for determining diagnostic accuracy.

The primary objective is to compare the diagnostic accuracy-measured by sensitivity, specificity, positive predictive value, and negative predictive value-of mid-end versus high-end ultrasound systems in detecting ileocolonic disease activity. The study aims to determine whether mid-end machines, which are more affordable and accessible, can offer comparable diagnostic performance to high-end systems.

Secondary objectives include assessing whether ultrasound findings lead to changes in clinical management. To ensure objectivity, an independent panel of three experienced inflammatory bowel disease physicians-blinded to the identity of the ultrasound machine-will review each case and determine whether ultrasound findings would have justified changes such as treatment escalation or de-escalation, surgical referral, or additional diagnostic evaluation. Panel decisions will be based on standardized clinical scenarios and will be adjudicated by consensus.

The study also includes a health-economic component, analyzing how the integration of mid-end ultrasound into clinical workflows may reduce reliance on invasive and high-cost diagnostics like colonoscopy or cross-sectional imaging. Real-world cost estimates will be used to model the economic impact.

By providing comparative data on diagnostic accuracy, management impact, and economic value, the HUMID Study seeks to inform clinical practice guidelines and promote the use of scalable ultrasound solutions in inflammatory bowel disease, particularly in resource-constrained healthcare settings.

Inclusion criteria

• Patients aged 18-75 years.
• Confirmed diagnosis of inflammatory bowel disease (IBD), specifically with ileocolonic involvement.
• Clinically stable at the time of assessment.
• Willing and able to undergo both intestinal ultrasound (IUS) assessments (mid-end and high-end) and the reference standard ileo-colonoscopy.
• Provides informed consent to participate in the study.

Exclusion criteria

• Pregnant or breastfeeding individuals.
• Patients with contraindications to ileo-colonoscopy (e.g., severe comorbidities, known intolerance).
• Individuals unable to provide informed consent.
• Patients with conditions interfering with ultrasound imaging, such as severe obesity or uncooperative behaviour