C3 and primary membranoproliferative glomerulonephritis: When compared to IC-MPGN, patients with C3GN had significantly lower C3 (32.9 vs. 88.0 mg/dL), C4 (18.1 vs. 24.0 mg/dL), and CH50 (31.7 vs. 43.5 U/mL) at the time of diagnosis.