P351 Validation of anterior thigh ultrasound for screening of sarcopenia and elevated body fat in Inflammatory Bowel Disease

Abstract Background Sarcopenia (low muscle mass, strength and function) and visceral obesity are associated with adverse outcomes in inflammatory bowel disease (IBD). US measurement of thigh muscle thickness as a biomarker of muscle loss in IBD has not been validated to date. Our aim is to validate anterior thigh US for measurement of total muscle thickness (TMT) and fat thickness (FT) in IBD patients and to identify muscle thickness values associated with sarcopenia using bioelectrical impedance analysis (BIA). Methods A prospective study of muscle function and mass was carried out using handgrip strength testing, sit-to-stand test, B-mode US and bioelectrical impedance analysis (BIA) (SECA mBCA 525) in IBD patients attending outpatients in our centre. Sarcopenia was confirmed by ASM/H2. Stata was used for statistical analysis, p ≤ 0.05 denoted statistical significance. Results A total of 52 patients were included, 42% (n=22) were females with a mean age of 45.5 years. CD patients accounted for 75% (n=39). Mean BMI of females was 29.64 (SD 5.88) vs males 26.2 (SD 3.8), p=0.014. Sarcopenia was diagnosed in 16 patients (31%), 10/16 were female with a significantly lower TMT vs non-sarcopenic females (mean 3.56cm vs 4.32cm, p=0.05). ASM/H2 was lower in sarcopenic patients (mean 4.67 kg/h2 vs 8.97 kg/h2, p<0.001). Handgrip strength was lower in sarcopenic patients (mean 24.4 vs 32.1 kg, p=0.25), sit-to-stand did not differ significantly (mean 18.84 vs 13.13sec, p=0.027). Physical activity levels were insignificantly lower in the sarcopenia group (mean PAL 1.78 vs 1.85, p=0.089). TMT strongly correlated with ASM/H2 (r=0.385,p=0.005), skeletal muscle mass (mm) (r=0.368, p0.008), right leg MM (r=0.404, p0.003), handgrip strength (0.29, 0.035) and BMI (r=0.39, 0.005). FT strongly correlated with body fat (kg) (r=0.699, p<0.001), body fat % (r=0.76, p<0.001), body fat index (r=0.67, p<0.001), waist circumference (r=0.35,p0.01) and BMI (r=0.68, p<0.001). Of the sarcopenic patients, 62.5% had high body fat (n=10) which trended toward but did not reach statistical significance (p=0.08). Visceral fat was high overall with higher levels in men (3.6L vs 2.0L, p=0.009), it did not correlate with SF (r=-0.074, p=0.6). Finally, the intra-rater reliability for TMT and SF were both excellent (r=0.97, p<0.001 and 0.979 p<0.001 respectively). Conclusion Sarcopenia is prevalent in IBD patients. Anterior thigh US correlates with BIA and can be used as a screening tool for early loss of muscle mass in IBD patients in addition to screening for high visceral adiposity. The presence of increased visceral adiposity was high, which may have deleterious outcomes for CD patients, given its association with transmural inflammation and post-operative recurrence.