Evaluation of Serum Complement C3 and C4 Levels in Disease Activity and Long-Term Prognosis of Systemic Lupus Erythematosus

WANG Yizhen; LUO Fei; FANG Hua; TANG Wentao; OU Jing

doi:10.3639/j.issn.2095-3097.2026.02.017

Abstract：Objective To investigate the evaluation value of serum complement C3 and C4 levels on disease activity and long-term prognosis of systemic lupus erythematosus(SLE).Methods A total of 108 patients with systemic lupus erythematosus(SLE)who attended Chizhou People's Hospital from February 2020 to June 2024 were selected retrospectively.They were divided into two groups based on prognosis:the good prognosis group(81 cases)and the poor prognosis group(27 cases).According to the SLE disease activity index score,the patients were categorized into the mild activity group(66 cases),the moderate activity group(31 cases),and the severe activity group(11 cases).The serum levels of complement C3 and C4 were compared among the three activity groups;receiver operating characteristic(ROC)curve analysis was used to evaluate the value of serum complement C3 and C4 levels in assessing SLE disease activity.General clinical data were compared between the two prognosis groups;multivariate logistic regression analysis was applied to identify the influencing factors of long-term prognosis in SLE patients;and ROC curve analysis was also used to assess the value of serum complement C3 and C4 levels in predicting the long-term prognosis of SLE patients.Results Compared with the mild activity group,serum complement C3 and C4 levels in the moderate activity group and the severe activity group were decreased(P<0.05).ROC curve analysis revealed that the areas under the curve(AUC)of serum complement C3,complement C4,and their combined detection(parallel mode)for evaluating disease activity in SLE patients were 0.679,0.786,and 0.912,respectively.The AUC of the combined detection was significantly superior to that of C3 or C4 alone(Z=3.210,2.870,P<0.05).Compared with the good prognosis group,the poor prognosis group had a higher incidence of organ involvement,poorer treatment adherence,elevated levels of immunoglobulin G(IgG),immunoglobulin A(IgA),and immunoglobulin M(IgM),as well as lower serum complement C3 and C4 levels(P<0.05).Multivariate logistic regression analysis revealed that the presence of organ involvement,elevated IgG,IgA and IgM levels and decreased complement C3 and C4 levels were independent risk factors for poor prognosis in SLE patients(OR=1.539,95%CI:1.069-2.216,P=0.021;OR=1.078,95%CI:1.030-1.128,P=0.001;OR=1.071,95%CI:1.028-1.116,P=0.001;OR=1.071,95%CI:1.024-1.121,P=0.003;OR=0.931,95%CI:0.887-0.978,P=0.005;OR=0.935,95%CI:0.885-0.988,P=0.017).For the evaluation of long-term prognosis in SLE patients,the AUC values of serum complement C3,complement C4,and their combined detection were 0.560,0.803 and 0.912,respectively.The AUC of the combined detection was significantly better than that of C3 alone(Z=4.010,P<0.001).Conclusion Serum levels of complement C3 and C4 and their combination have good evaluation value for disease activity and long-term prognosis in SLE patients.The presence of organ involvement,elevated IgG,IgA,IgM,and decreased serum complement C3 and C4 levels are risk factors affecting the long-term prognosis of SLE patients.