Complement 1q (C1q) antibodies levels in sera of Egyptian patients with lupus nephritis.

Renal involvement is common in systemic lupus erythematosus (SLE). Anti-C1q antibodies are associated with SLE nephritis. This study attempted to correlate anti-C1q levels to different types of lupus nephritis (LN). Anti-C1q antibodies were assessed in two groups (15 subjects each) of SLE patients with and without LN. Ten apparently healthy volunteers served as controls. The sensitivity of anti C1q for diagnosis of lupus nephritis among SLE patients was 100.00% and the specificity reached 90.00%. The positive and negative predictive values for renal activity were 83.3% and 100.00%, with a predictive accuracy of 98.00%. The level of anti C1q was highest in patients with class IV lupus nephritis. We conclude that negative anti- C1q test results would exclude active nephritis in SLE. Our data support the hypothesis that anti-C1q antibodies may have pathogenic role in lupus nephritis.