Evaluation of Serum Leucine-Rich α2-Glycoprotein Levels in Inflammatory Bowel Disease Patients Across Racial Groups

Background Serum leucine-rich alpha-2 glycoprotein (LRG) has emerged as a novel biomarker for inflammatory bowel disease (IBD). However, its clinical utility among non-Japanese populations has not been investigated. This study aimed to validate the diagnostic ability of serum LRG in non-Japanese patients with IBD. Methods A retrospective cross-sectional study was conducted. Patients with IBD who underwent at least one serum LRG measurement between 2020 and 2023 were included. Correlations between serum LRG and C-reactive protein (CRP) level was evaluated separately for Japanese and non-Japanese cohorts. Serum LRG levels were compared based on endoscopic severity status. The diagnostic ability of LRG for predicting endoscopic activity was evaluated by receiver operating characteristic (ROC) analysis. Results Serum LRG levels were measured at 11,730 time points for 2,500 Japanese patients, and 276 time points in 58 non-Japanese patients. Among non-Japanese patients, 53% were Asian, 37% White, 4% Black, and 6% other racial background. The correlation between LRG and CRP was similarly robust in non-Japanese (r = 0.64) and Japanese (r = 0.64) patients. Among non-Japanese, serum LRG levels in endoscopic remission was significantly lower than those in active disease (P = 0.0009). Area under the ROC curve of LRG for endoscopically active disease in ulcerative colitis (n = 46) was 0.78 (95% confidence interval (CI), 0.65–0.92), superior to that of CRP at 0.63 (95% CI, 0.46–0.79). Conclusion Serum LRG is a reliable biomarker for assessing disease activity in both non-Japanese and Japanese IBD patients, supporting its broader clinical applicability across diverse populations.