Optimal use of serum leucine-rich alpha-2 glycoprotein as a biomarker for small bowel lesions of Crohn's disease

Abstract A large proportion of small bowel lesions in Crohn’s disease (CD) may exist beyond the scope of ileocolonoscopy, suggesting the need for optimal biomarkers. This cross-sectional observational study prospectively measured C-reactive protein (CRP), faecal calprotectin (FC), and leucine-rich alpha-2 glycoprotein (LRG) in patients with quiescent CD who underwent imaging examinations (capsule or balloon-assisted endoscopy, magnetic resonance enterography, or intestinal ultrasound). Mucosal healing (MH) of the small bowel was defined as a lack of ulcers. Patients with a Crohn’s disease activity index of >220 and active colonic lesions were excluded. Seventy patients (29, MH; 41, small bowel inflammation) were analysed. The area under the curve (AUC) of CRP, FC, and LRG was 0.74 (95% confidence interval 0.60-0.86), 0.68 (0.52-0.80), and 0.75 (0.58-0.84), respectively. A cut-off of 16 μg/ml of LRG showed the highest positive predictive value of 0.95 with a specificity of 0.96, while the negative predictive value was the highest (0.71) with a sensitivity of 0.90 at a cut-off of 9 μg/ml. This suggests that LRG can accurately detect and/or exclude the small bowel lesions using two cut-off values.