C4A and systemic lupus erythematosus: Compared with non-crescent group, MBP (P < 0.001), serum creatinine (P < 0.001), WBC count (P = 0.019), 24-h proteinuria (P < 0.001), urinary ACR (P < 0.001), urine WBC count (P < 0.001), urine RBC count (P < 0.001), proportion of positive anti-dsDNA antibodies (P < 0.001), and SLEDA index (P < 0.001) were higher, while eGFR (P < 0.001), serum albumin (P = 0.001), hemoglobin (P < 0.001), complement C3 (P = 0.007), complement C4 (P = 0.015), and lupus anticoagulant ratio (P < 0.001) were lower in crescent group.