C4A and systemic lupus erythematosus: Additionally, we stratified the complement C3 and C4 serum levels according to cardiovascular risk by CRP, and we did not observe significant differences in C3 according to CRP levels, but we found a tendency for lower C4 levels in SLE patients with average (≥1 mg/L) and high cardiovascular risk (≥3 mg/L) compared to SLE patients with low risk (<1 mg/L) (CRP low risk: 25.2 mg/dL; average risk: 12.5 mg/dL; high risk: 15.5 mg/dL; p = 0.06).