C4A and systemic lupus erythematosus: Another study demonstrated that D-dimer levels were positively correlated with the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI), and were associated with factors such as anti-dsDNA antibodies, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), and complement components C3 and C4, as well as multi-organ involvement [11].