Usefulness of complement activation products in Chinese patients with systemic lupus erythematosus

Objective To evaluate the roles of complement activation products C3d and C4d binding to lymphocytes in the diagnosis of systemic lupus erythematosus (SLE) in a cohort of Chinese patients. Methods 96 patients with SLE, 44 patients with other autoimmune disease and 40 healthy control individuals were enrolled in this study. The levels of C3d and C4d binding to peripheral CD4(+) T and CD19+ B lymphocyts (designated as T-C3d, T-C4d, B-C3d, B-C4d) was assessed by flow cytometry. The diagnostic values of these biomarkers were determined by receiver-operator characteristic analysis. Results The levels of T-C3d, T-C4d, B-C3d, B-C4d were significantly higher in SLE patients than patients with other disease and healthy controls (p<0.01). As diagnostic tools, T-C4d and B-C4d were 61.1% sensitive 194.3% specific and 63.9% sensitive 194.3% specific in differentiating SLE patients from patients with other disease and healthy controls, respectively. T-C4d and B-C4d were significantly associated with SLE disease activity as measured by the SLE disease activity index (SLEDAI) (p<0.001), low serum C3 (p<0.001), low serum C4 (p=0.006), anti-dsDNA (IF) (p=0.001), and anti-dsDNA (ELISA) (p=0.001). Conclusion Complement activation products C3d and C4d binding to lymphocytes can reflect the disease activity of SLE and can be used as biomarkers for SLE.