Correlation study between complement C3 level and degree of disease activity in patients with systemic lupus erythematosus

Abstract

Objective To investigate the relationship between complement C3 level and the degree of disease activity in patients with systemic lupus erythematosus(SLE). Methods A total of 1 012 patients with SLE were enrolled in this study from January 2006 to December 2013 at department of rheumatology and immunology, the first affiliated hospital of Anhui medical university. Serum complement C3 level was detected by rate erythenephelometry assay. The relationship between reduction of complement C3 and SLE was analyzed. Results Serum complement C3 clearly decreased in 782 patients, accounted for 77.27%. There were significant differences concerning serum complement C3 level among different groups of disease activity (F=131.275, P<0.01). The low serum complement C3 level was correlated with the high degree of disease activity (r=-0.517, P<0.01). Patients with SLE had a severe disease activity (SLE disease activity index ≥15) when the level of serum complement C3 was less than 0.57 g/L. Serum complement C3 levels were positively correlated with serum complement C4 (r=0.845, P<0.01), peripheral blood leukocyte count (r=0.115, P<0.01), hemoglobin (r=0.069, P<0.01), platelet count (r=0.177, P<0.01) and albumin level (r=0.091, P<0.01). There was also a negative association of serum complement C3 with 24 h urinary protein (r=-0.228, P<0.01). 101 patients whose average level of serum complement C3 was(0.48±0.26)g/L, were treated with glucocorticoid pulse therapy as high degree of disease activity. Conclusions There is a close relationship between serum complement C3 level and the degree of disease activity in SLE. Serum complement C3 less than 0.57 g/L might be seen in SLE with severe disease activity. Key words: Lupus erythematosus, systemic; Complement system proteins; Disease activity