Leucine-rich alpha-2 glycoprotein as a superior biomarker to C-reactive protein for detecting small bowel lesions in Crohn's disease.

Background: Achievement of endoscopic healing (EH) is significant in the clinical practice of inflammatory bowel disease as it is correlated with improved prognosis. Existing biomarkers, including C-reactive protein (CRP), have relatively low accuracy for predicting EH, especially in small intestinal lesions in Crohn's disease (CD); thus, noninvasive and more accurate biomarkers are required. Leucine-rich alpha-2 glycoprotein (LRG), a 50-kD protein, is produced under inflammatory conditions and has been reported to be useful in assessing disease activity in inflammatory bowel disease. However, the usefulness of LRG in small intestinal lesions in CD remains inconclusive.

Aim: To determine the usefulness of LRG for EH in small bowel lesions in CD and compare it with CRP.

Methods: This study included 133 consecutive patients with CD who underwent balloon-assisted enteroscopy between June 2021 and March 2024 at Shiga University of Medical Science Hospital (Otsu, Japan). We retrospectively analyzed endoscopic scores in each of the ileum and colon and four markers including LRG, CRP, albumin, and Harvey-Bradshaw index (HBI). Spearman's rank correlation coefficient and receiver operating characteristic analysis were performed.

Results: Either active ileal or colonic lesions exhibited significant differences in LRG, CRP, albumin, and HBI compared with EH. CRP, albumin, and HBI showed a worse correlation with endoscopic activity in the ileum than that in the colon; however, LRG did not show a worse correlation (colon, = 0.5218; ileum, = 0.5602). Receiver operating characteristic analysis revealed that LRG for EH in the ileum and colon had the same cutoff values of 12.4 μg/mL. Comparing the areas under the curve of LRG and CRP for predicting EH in the ileum revealed a significantly higher areas under the curve of LRG (95% confidence interval, 0.017-0.194; = 0.024), whereas the two showed no significant difference in the colon.

Conclusion: LRG is a useful biomarker in assessing the endoscopic activity of CD and is more useful than CRP in the small intestine.