Usefulness of Serum Leucine-rich Alpha 2 Glycoprotein in Crohn's Disease: Is There Any Difference between Small Intestine and Colonic Lesions?

Lay Summary The superiority of leucine-rich alpha 2 glycoprotein (LRG) to C-reactive protein (CRP) differs between small intestinal and colonic lesions. For Crohn's disease patients with ileum-dominant activity, monitoring of both LRG and CRP is necessary, instead of monitoring CRP alone. Background The usefulness of leucine-rich alpha 2 glycoprotein (LRG) to evaluate Crohn's disease (CD) activity differs among various intestinal lesions. We aimed to evaluate the association between endoscopic disease activity based on the Simple Endoscopic Score for Crohn's disease (SES-CD) and LRG level separately for small intestinal and colonic lesions. Methods We examined the correlation between LRG level and SES-CD and performed receiver operating characteristic (ROC) analysis to determine the LRG cutoff value in 141 patients who underwent endoscopy (total 235 measurements). Furthermore, the LRG cutoff value was analyzed by comparing small intestinal and colonic lesions. Results LRG levels were significantly higher in patients without mucosal healing than in those with mucosal healing (15.9 mu g/mL vs 10.5 mu g/mL, P < .0001). The LRG cutoff value for mucosal healing was 14.3 mu g/mL (area under the ROC curve [AUC]: 0.80; sensitivity: 0.89; specificity: 0.63). The LRG cutoff value for patients with type L1 was 14.3 mu g/mL (sensitivity: 0.91; specificity: 0.53), and that for patients with type L2 was 14.0 mu g/mL (sensitivity: 0.95; specificity: 0.73). The diagnostic performance (AUC) of LRG and C-reactive protein (CRP) for mucosal healing was, respectively, 0.75 and 0.60 (P = 0.01) in patients with type L1 and 0.80 and 0.85 (P = 0.90) in patients with type L2. Conclusions The optimal LRG cutoff value for evaluating mucosal healing in CD is 14.3 mu g/mL. LRG is more useful than CRP for predicting mucosal healing in patients with type L1. The superiority of LRG to CRP differs between small intestinal and colonic lesions.