Abstract: Objective To explore the significance of serum bilirubin in the evaluation of disease activity in patients with lupus nephritis (LN). Methods From May 2016 to September 2018, a total of one hundred systemic lupus erythematosus (SLE) patients as well as fifty healthy volunteer were enrolled in this study. SLE patients were divided into SLE group（n=50）and LN group（n=50）with or without renal damage. Variance analysis was used to analyze the differences of serum total bilirubin（TBIL）, direct bilirubin（DBIL）and indirect bilirubin（IBIL）levels. Pearson correlation analysis was employed to further identify the correlation of these factorsand SLE disease activity index（SLEDAI）score, cystatin C（CysC）and C-reactive protein（CRP）. Multivariate logistic regression analysis further analyzed the correlation between serum bilirubin and LN. ROC curve evaluated the sensitivity and specificity of TBIL, IBIL and DBIL in the diagnosis of LN. Results The levels of TBIL and IBIL were significantly lower in SLE group and LN group than HC group（P<0.05）, and the levels of TBIL, IBIL and DBIL also significantly lower in LN group than SLE group（P<0.05）.In LN group, TBIL, IBIL and DBIL level was respectively negatively correlated with SLEDAI score, CysC level and CRP concentration[（r=-0.489,P<0.05;r=-0.427,P<0.05;r=-0.381,P<0.05）,（r=-0.512,P<0.05;r=-0.423,P<0.05;r=-0.375,P<0.05）,（r=-0.398,P<0.05;r=-0.324,P<0.05;r=-0.318,P<0.05）].TBIL、IBIL、DBIL were protective factors for the pathogenesis of LN;The sensitivity of TBIL, IBIL and DBIL for the diagnosis of LN was 80.00%, 78.00% and 50.00%, and the specificity was 78.00%, 76.00% and 80.00%, respectively. Conclusion Bilirubin level can be used as a new biomarker to evaluate the degree of LN disease activity and renal function injury.

Key words: Lupus nephritis, Serum bilirubin, Cystatin C, New biomarker