P264 The utility of ANCA in Ulcerative Colitis and Crohn’s Disease: A Retrospective Cohort Study in Taiwan

Background Inflammatory bowel disease (IBD) includes two chronic idiopathic inflammatory diseases: ulcerative colitis (UC) and Crohn disease (CD). The diagnosis of IBD depends on clinical, endoscopic, histological, radiological and biochemical criteria, which may be invasive, time consuming and usually not accepted by patients with IBD. Antineutrophil cytoplasmic antibodies (ANCAs) is believed to be related to IBD. The aim of this study was to investigate these serological markers and the evidence for their use in the diagnosis and management of IBD in Taiwan. Methods We conducted a retrospective cohort study in adult IBD patients who had received the serum examinations using the medical records of China Medical University Hospital between 1 January 1980 and 31 October. 2023. Results A total of 301 IBD patients (194 with UC, 107 with CD) were included in this current study. A high proportion were male (IBD 70.41%; UC 65.63%, and CD 76.71%). The mean diagnostic age of these enrolled patients was 42.9 years. In our patients, the prevalence of positive anti-HCV Ab is 0.0% in UC patients and 0.96% in CD patients. However, the prevalence of positive HBsAg was 14.5% in UC patients and 9.4% in CD patients. The prevalence of pANCA was 21.2% in UC patients and 1.4% in CD patients, respectively. The prevalence of cANCA was 3.1% in UC patients and 0.0% in CD patients. This pattern of low sensitivity and high specificity for pANCA is also seen in UC patients in various cohort studies. The serum positivity of p-ANCA was significantly higher in UC patients (Figure 1). UC patients with positive p-ANCA were older than CD patients with positive p-ANCA (44.9 vs. 37.3 years). Furthermore, we found that the incidence of positive p-ANCA in UC patients with E1, E2, and E3 at diagnosis was 3.5%, 39.2%, and 57.1%, respectively (Table 1). The serum levels of ANCA-IgG were indeed higher in patients in the severe group than those in the moderate and mild groups. Conclusion Serological biomarkers have been demonstrated to be a series of rapid, non-invasive approaches for assessments of early diagnosis, disease activity and prognosis for IBD. ANCA may be helpful in the early diagnosis of UC and in differentiating it from CD. UC patients with positive ANCA have a higher rate of intestinal mucosal vasculitis than UC patients with negative ANCA. Furthermore, ANCA may also contributes to the pathogenesis of HBV-related systemic vasculitis. Therefore, the management of HBV-related vasculitis includes control the immune complex formation and reaction as well as antiviral agents to reduce the antigenic load resulting in reduction of inflammation. Moreover, effective biomarkers with high sensitivity and specificity need to be investigated in the future.