ABSTRACT
Objective To explore the value of serum SC5b-9, anti-C1q antibody, C3 and C4 levels in the assessment of lupus activity. Methods The enzyme linked immunosorbent assay (ELISA) was used to measure SC5b-9 and anti-C1q antibody, rate nepheiometry was used to detect the serum level of C3 and C4 in sera of 62 SLE patients, 35 patients with other rheumatic diseases (including rheumatoid arthritis, ankylosing spondylitis, primary Sjogren' s syndrome, mixed connective tissue disease, dermatomyositis, polymyositis, systemic sclerosis and vasculitis) and 35 healthy controls. And the correlation between above-mentioned parameters and lupus clinical manifestations, disease activity and histological type of lupus nephritis were analyzed. Results In SLE patients, the levels of SC5b-9 and anti-C1q antibody were significantly higher than those in patients with other rheumatic diseases and healthy controls (P<0.05). The titers of SC5b-9 and anti-C1q antibody negatively correlated with C3 and C4 (P<0.05), and positively correlated with SLEDAI (P<0.05). The sensitivity and specificity of the combination of these three measurements for SLE was 95.37% and 98.46 respectively. SC5b-9 and anti-C1q antibody were associated with the presence of proliferative glomerulonephritis (P <0.05). Conclusion Taking the evaluation of all these three measurements simultaneously is valuable for the diagnosis of lupus flare. SC5b-9 and anti-C1q antibody may play major roles in the immunopathogenesis of lupus nephritis.