Effect of Disease Extent on Leucine‐Rich α2 ‐Glycoprotein as a Marker for Endoscopic Mucosal Healing in Patients With Ulcerative Colitis

Aims To determine whether the performance of leucine‐rich α2‐glycoprotein (LRG) as a biomarker for disease activity in patients with ulcerative colitis (UC) may depend on the extent of the disease. Methods and Results We evaluated the correlation between various biomarkers, including the serum biomarker LRG, and endoscopic activity in 171 patients with UC. Patients were categorized into two groups based on disease extent: patients with pancolitis and those with left‐sided colitis and proctitis. LRG demonstrated similar diagnostic accuracy compared to fecal markers in patients with UC exhibiting pancolitis (area under the curve [AUC] for predicting endoscopic mucosal healing: LRG, 0.92; fecal immunochemical testing [FIT], 0.95; and fecal calprotectin [Fcal], 0.96) (FIT vs. LRG, p = 0.886; Fcal vs. LRG, p = 0.412). Conversely, for patients with left‐sided colitis and proctitis, fecal markers outperformed LRG in predicting endoscopic mucosal healing (AUC: LRG, 0.66; FIT, 0.94; and Fcal, 0.92) (FIT vs. LRG, p < 0.001; Fcal vs. LRG, p = 0.004). Conclusion Our results support selecting biomarkers according to disease extent for the management of inflammatory bowel disease. In patients with UC and pancolitis, LRG is a viable alternative when fecal samples are not feasible. Conversely, for patients with left‐sided colitis and proctitis, fecal markers with high diagnostic accuracy are recommended.