Supplementary Material for: A Polymorphism in <b><i>Interleukin-1β</i></b> Gene Is Associated with the Development of Pouchitis in Japanese Patients with Ulcerative Colitis

<b><i>Background:</i></b> Major complications in patients with ulcerative colitis (UC) include UC-associated cancer (UCAC) and postoperative pouchitis. We aimed to identify SNPs associated with UCAC/high-grade dysplasia (HGD) and pouchitis. <b><i>Methods:</i></b> Patients with UC who underwent ileal pouch-anal anastomosis (IPAA) with &gt;2 years of follow-up after functioning pouches were included. Pouchoscopies were performed at least once to diagnose pouchitis according to the modified pouchitis disease activity index. SNP genotyping was performed for 8 SNPs reportedly associated with UCAC and pouchitis, namely: <i>ELF1</i> (rs7329174), <i>FCGR2A</i>, (rs1801274), interleukin-1β (<i>IL-1B</i>; rs1143627), <i>ITLN1</i> (rs2274910), <i>MHC</i> (rs7765379), <i>TNFα</i> (rs1799964), <i>TNFSF15</i> (rs3810936), and <i>UHMK1</i> (rs768910), using TaqMan genotyping technologies. We investigated the association of these SNPs with UCAC/HGD and pouchitis. Patients’ background data were retrospectively collected, including the presence of preoperative extraintestinal manifestation (EIM). <b><i>Results:</i></b> A total of 91 Japanese patients with UC were included. None of the 8 SNPs were associated with UCAC/HGD in our cohort. Multivariable analyses proved that the presence of preoperative EIM (hazard ratio [HR] 3.313, 95% CI 1.325–8.289) and <i>IL-1B</i> (rs1143627) TT genotype (HR 2.425, 95% CI 1.049–5.61) were independent predictive factors for the development of overall pouchitis. The presence of preoperative EIM (HR 3.977, 95% CI 1.292–12.24) and <i>IL-1B</i> (rs1143627 TT genotype; HR 3.382, 95% CI 1.101–10.39) were also independent predictive factors for the development of chronic pouchitis. <b><i>Conclusions:</i></b> The <i>IL-1B</i> (rs1143627) TT genotype and preoperative EIM were statistically significant predictors of pouchitis development after IPAA in patients with UC.