783 Nonalcoholic Fatty Liver Disease in a South Asian Crohn's Disease Population: External Validation of the St. Louis Steatosis Index

INTRODUCTION: Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease affecting one-quarter of the world population. NAFLD is also an extra-intestinal manifestation of Crohn's Disease (CD), where it is associated with higher morbidity and mortality. We aimed to (1) characterize risk factors for NAFLD in South Asian CD pts, and (2) externally validate a clinical prediction score for NAFLD in CD, the St. Louis Steatosis Index (SLSI). METHODS: We prospectively enrolled CD pts from 2/1/2019-5/31/2019 at the Asian Institute of Gastroenterology, a tertiary referral center for Inflammatory Bowel Disease (IBD) in India. Exclusion criteria included an alternative etiology of liver disease (e.g., chronic viral hepatitis). Controlled attenuation parameter (CAP) with transient elastography was measured using FibroScan® (Echosens, Waltham, MA) to quantitate hepatic steatosis and fibrosis. The outcome of NAFLD was defined as CAP ≥ 240 dB/m with the secondary outcome of hepatic fibrosis defined as ≥7 kPa. The SLSI operating characteristics were compared at re-calibrated low risk (<10%) and high risk (>40%) thresholds. The discrimination was compared to the Hepatic Steatosis Index (HSI) by both the C-statistic and net reclassification improvement (NRI) for the primary outcome and to both the HSI and the NAFLD fibrosis score (NFS) for the secondary outcome. RESULTS: 100 pts (63% male, median age 35 years) were enrolled with 42 (42%) demonstrating NAFLD and 6 (6%) demonstrating hepatic fibrosis. Univariate risk factors for NAFLD are shown (Table 1). Older age, male gender, elevated BMI, and presence of hypertension were significantly associated with a diagnosis of NAFLD. A low-risk SLSI was 71% sensitive and a high-risk SLSI was 93% specific for a diagnosis of NAFLD. SLSI showed fair discrimination for NAFLD but this was not different from the HSI (C statistic 0.747 vs 0.722; NRI +0.02). For the diagnosis of hepatic fibrosis, a low-risk SLSI was 83% sensitive and a high-risk score was 90% specific. The SLSI showed fair discrimination (0.767) that was superior to both the HSI (C statistic 0.587, NRI +0.47) and the NFS (C statistic 0.688, NR +0.23). CONCLUSION: NAFLD was common among this South Asian cohort with CD despite few traditional risk factors. The SLSI has fair discrimination for both NAFLD and the more clinically relevant subgroup with hepatic fibrosis. Further steps include exploring alternate mechanisms for this finding and devising more sensitive CD-specific screening tools for NAFLD.