P0552Plasma Galactose-Deficient IgA Correlates with Intestinal Ultrasound Parameters in Inflammatory Bowel Disease

Abstract Background IgA is an important immunoglobulin involved in gut mucosal immunity, and pathogens defense. It had a specific form that is glycan deficient: Galactose-deficient IgA (Gd-IgA). Our previous study demonstrated that plasma IgA and Gd-IgA correlated with disease activity, measured by erythrocyte sedimentation rate (ESR) and the Partial Mayo score, in ulcerative colitis (UC)1,2. Intestinal ultrasound (IUS) is an established tool for monitoring disease activity in inflammatory bowel disease (IBD) and can reflect the severity of bowel wall inflammation. The association between IUS parameters and plasma IgA or Gd-IgA remains unclear. We aimed to investigate the relationship between bowel wall inflammation by IUS between IgA and Gd-IgA. Methods We enrolled IBD patients with regular IUS examination between 2023 and 2025 at China Medical University Hospital. Plasma IgA and other biological markers were assessed alongside with assessment of IUS evaluation in patients with or without advanced therapy (adalimumab, vedolizumab and JAK inhibitors). Gd-IgA was measured by ELISA kit (Immuno-Biological Laboratories Co., Ltd.). Statistical analysis was performed using Student’s t-test and linear regression. Results We enrolled 32 UC and 12 Crohn’s disease patients (Table 1). We found that Plasma Gd-IgA, but not total IgA, showed a positive correlation with bowel wall thickness (BWT), Gd-IgA1 has a stronger positive correlation compared to total IgA (Figure 1A). Gd-IgA levels were significantly higher in IBD patients with BWT 3 mm compared with those with BWT ≤3 mm (Figure 1B). Similarly, patients with positive bowel wall flow (BWF) exhibited higher Gd-IgA levels than those without BWF, consistent across both UC and CD cohorts (Figure 1C). Finally, plasma Gd-IgA level was positively correlated with Milan ultrasound criteria (MUC) and the Bowel ultrasound score (BUSS) score (Figure 1D). Conclusion Plasma GdIgA but not total IgA, correlates with intestinal ultrasound parameters, particularly BWT and BWF. Moreover, both the MUC and the BUSS scores show positive associations with Gd-IgA. These findings suggest that plasma GdIgA reflects bowel wall inflammation, especially with blood flow activity, as detected by IUS and may serve as a complementary serological marker for the monitoring of inflammatory bowel disease. References: 1. Tsai T, Hsu JL. P0459 Plasma IgA as a biomarker and IL-21 as a potential therapeutic target in Inflammatory Bowel Disease. J Crohns Colitis. 2025;19(Suppl 1):i981–i982. doi:10.1093/ecco-jcc/jjae190.0633. 2. Tsai T, Hsu JL. O1301 Exploring the role of galactosedeficient IgA in ulcerative colitis: from biomarker potential to cytokinedriven mechanisms. Presented at: 13th Annual Meeting of the Asian Organization for Crohn’s and Colitis (AOCC 2025); July 10–12, 2025; Chiba, Japan. Confit. Accessed October 4, 2025. https://pub.confit.atlas.jp/en/event/aocc2025/presentation/26001 Conflict of interest: Prof. Dr. Tsai, Tsungyu: No conflict of interest