Serum leucine-rich α2-glycoprotein is elevated in patients with systemic lupus erythematosus and correlates with disease activity

Background: We evaluated whether serum leucine-rich α2-glycoprotein (LRG) is associated with disease activity in patients with systemic lupus erythematosus (SLE). Methods: We measured serum LRG in 194 SLE patients. SLE disease activity index-2000 (SLEDAI-2 K) was used to assess SLE activity, and patients with SLEDAI-2 K ≥5 were defined as having active SLE. Correlation between serum LRG, SLEDAI-2 K, and laboratory variables was estimated by Pearson's correlation analysis. The optimal serum LRG cut-off value for predicting active SLE was calculated using receiver operator characteristic (ROC) curve, and multivariable logistic regression was used to determine the odds ratio (OR) of laboratory variables. Results: In total, 74 (38.1%) and 120 (61.9%) patients were classified as active and inactive SLE, respectively. Serum LRG was higher in patients with active SLE than in inactive SLE and healthy controls (26.6 vs. 14.4 vs. 1.2 ng/ml, p <.001). Serum LRG significantly correlated with SLEDAI-2 K (r = 0.340, p <.001) and laboratory variables. ROC analysis revealed that optimal serum LRG cut-off value for active SLE was >45.7 ng/ml. In multivariable logistic regression analysis, serum LRG >45.7 ng/ml (OR 4.089, 95% confidence interval 1.351, 12.376, p =.013) was an independent predictor of active SLE. Conclusions: Serum LRG might be a biomarker for estimating SLE disease activity.