Determining the accuracy and interobserver agreement of four ultrasound scores in Crohn's disease assessment: correlations with endoscopy

Background: Gastrointestinal ultrasound (GIUS) is recommended for monitoring Crohn's disease (CD). GIUS scores are used to quantify CD activity. Among them, IBUS-SAS (International Bowel Ultrasound Segmental Activity Score), BUSS (Bowel Ultrasound Score), Simple-US (Simple Ultrasound Score), and SUS-CD (Simple Ultrasound Score for Crohn's Disease) are most commonly used. This study aimed to compare and correlate the performance of such indicators with endoscopic activity and to calculate interobserver agreement.

Methods: Consecutive CD patients at our hospital between June 2015 and July 2021 were retrospectively enrolled. All patients underwent ileocolonoscopy after medical treatment. GIUS was performed within 2 weeks and four GIUS scores were independently calculated. Receiver operating characteristic (ROC) curve analyses were used to determine a cut-off value. Cohen's kappa(κ) coefficient was calculated to estimate the agreement between GIUS findings.

Results: A total of 106 CD patients were enrolled. 80.2% (85/106) were endoscopic active (SES-CD≥3), and 8.49% (9/106) were severe cases (SES-CD≥9). All GIUS features (bowel wall thickness, color doppler signs, bowel wall stratification, inflammatory signals at the mesentery) were statistically significant in assessing CD activity (p<0.05). IBUS-SAS showed the highest AUC (0.98; 95% CI:0.96-1.00) and specificity (95.2%) for a cut-off value of 46.50. However, IBUS-SAS had only moderate agreement (Cohen's κ=0.427; p<0.001). BUSS had substantial interobserver agreement (Cohen's κ=0.947; p< 0.001), with a similar diagnostic value [sensitivity, 100.0%; accuracy, 95.3%; AUC of 0.96(95% CI:0.91-1.00) for a cut-off value of 4.58].

Conclusions: GIUS score is an efficient and reliable method to assess CD activity. BUSS achieved a high accuracy and excellent interobserver agreement, which is more suitable for treatment assessment.