Abstract
BACKGROUND AND OBJECTIVE: Leucine-rich alpha-2 glycoprotein (LRG) is a novel biomarker for Crohn's disease (CD). The utility of combination use of LRG and C-reactive protein (CRP) has not been reported. This study aimed to investigate the diagnostic performance of LRG in combination with CRP to predict endoscopic activity. METHODS: A single-centre, retrospective, cross-sectional study was conducted. Patients with CD who had serum LRG concentrations measured at least once between June 2020 and May 2021 were enrolled. Clinical activity was evaluated with the Harvey-Bradshaw Index (HBI). Spearman's rank correlation coefficient (r(s)) was used to analyse the correlations between the HBI, LRG concentrations and CRP concentrations. In patients undergoing ileocolonoscopy or balloon-assisted enteroscopy within 60 days before or after LRG measurement, endoscopic activity was evaluated with the simple endoscopic score for Crohn's disease (SES-CD). The diagnostic performance of LRG and CRP for endoscopic activity was evaluated using receiver operating characteristic (ROC) analysis. RESULTS: Four hundred and eighty-nine measurements in 343 patients were analysed. Although a strong correlation was found between LRG and CRP concentrations (r(s) = 0.75), the HBI did not well correlate with LRG or CRP concentrations. Endoscopic activity was analysed in 56 patients. In diagnosing endoscopically moderate to severe activity (SES-CD > 6), the area under the ROC curve of LRG was greater than that of CRP (0.74 vs. 0.63; p = .037). The optimal cut-off value estimated by Youden's index was 15.5 µg/mL for LRG, and 0.13 mg/dL for CRP. LRG and CRP concentrations were considered positive when they were above these cut-off values, and the sensitivity and specificity for an SES-CD > 6 were 58.3% and 93.8%, respectively. Dual positivity of LRG and CRP showed the highest specificity. CONCLUSIONS: Combination use of dual positive LRG and CRP is useful for diagnosing endoscopically moderate to severe disease.