P466 Ultrasound muscle assessment for sarcopenia screening in patients with Inflammatory Bowel Disease: A prospective study (SarcUS-IBD)

Sarcopenia is prevalent among patients with Inflammatory Bowel Disease (IBD) and impacts IBD patient’s surgical and therapeutic outcomes, thus necessitating effective diagnostic tools to assess muscle mass and function in this population. A total of 153 consecutive patients were enrolled, 100 in the "training cohort" and 53 in the "study cohort". Three superficial muscles (Rectus Femoris (RF), Rectus Abdominis (RA) and Biceps Brachii (BB)) were chosen for sarcopenia detection with muscle ultrasound (US). The "training cohort" served for feasibility and interobserver variability assessment of US measurement. In the "study cohort", muscle ultrasound (US), bioelectrical impedance analysis (BIA), and magnetic resonance imaging (MRI) were employed to measure muscle parameters. BIA served as the reference standard for comparison. Accuracy of a self-reported questionnaire for sarcopenia screening was assessed. The prevalence of sarcopenia in IBD patients was 50%. Muscle US demonstrated good diagnostic accuracy in detecting sarcopenia compared to BIA, with Area Under the Receiver Operating Characteristic Curve (AUROC) values of 80% and 85% for RA and BB thickness, respectively. Moreover, an Ultrasound Muscle Index (USMI) was defined by the sum of RA, BB, and RF thickness measurements divided by the square of the patient's height, resulting in an AUROC of 81%. Several muscle cutoffs for sarcopenia were recognized, with those of RA and USMI being correlated with the highest positive (84.3%) and negative (99%) predictive values, respectively. Excellent inter-rater and intra-rater reliability (ICC > 0.95) were observed for US measurements. Additionally, the agreement between the US and magnetic resonance measurements of rectus abdominis was excellent (ICC 0.96). The findings of this study emphasize the potential of muscle US as a reliable diagnostic tool for assessing sarcopenia in IBD patients. The study provides cutoff values for US measurements, aiding clinicians in accurate diagnosis. Self-reported questionnaires showed limitations in identifying sarcopenia, underlining the importance of objective measures like US or BIA. Muscle loss in IBD patients appears to be associated with disease activity rather than systemic inflammatory markers. This research has significant implications for disease management in IBD patients and underscores the need for further investigations with larger cohorts and long-term follow-ups to validate these findings.