P321 Development and validation of an Integrated Risk Score for future risk of Crohn’s disease in healthy first-degree relatives: The CCC-GEM Project, a multicentre prospective cohort study

Abstract Background Although the cause of Crohn’s disease (CD) is unknown, recent studies have identified a number of biomarkers associated with the risk of developing CD in healthy at-risk individuals. Establishing a combined prediction model that stratifies the future risk of CD in healthy at-risk individuals is the first step towards disease prevention and a better understanding of the preclinical phase of CD. Methods We recruited healthy first-degree relatives (FDRs) of persons with CD from 2008-2017 as part of the global multicenter prospective Crohn’s and Colitis Canada Genetic Environmental Microbial (CCC-GEM) Project. After collecting demographic information, blood, urine, and stool samples at recruitment, participants were followed for the development of CD. A GEM-integrative risk score (GEM-IRS), using random survival forest modeling that combined the baseline variables (demographics, measures of gut inflammation – fecal calprotectin, intestinal barrier function – urinary fractional excretion ratio of lactulose to mannitol, and fecal microbiome composition and predicted functional capacities – based upon 16S rDNA sequencing and PICRUSt2) to estimate time-to-CD onset, was derived and subsequently validated in two independent testing cohorts. Results Among 2,619 FDRs followed for a median of 6.8 years, 61 (2.3%) developed CD. The GEM-IRS, developed on the training cohort (n= 1,170), upon validation, showed a c-statistic of 0.789 in the pooled-testing cohorts (0.786 in the North American Testing cohort (n=1,141) and 0.804 in the Israeli Cohort (n=308)). The 4th quartile group compared to the rest had significantly increased risk of CD (hazard ratio [HR] 6.42, 95% confidence interval [CI], 3.10-13.30) in the pooled-testing cohorts (HR 5.89, 95% CI, 2.70-12.85 in North American Testing cohort; HR 10.7, 95% CI 1.24-92.65 in Israeli cohort). Furthermore, the GEM-IRS predicted CD in pre-specified subgroups of FDRs with minimal subclinical inflammation (fecal calprotectin