C3 and systemic lupus erythematosus: Immunological workup for SLE showed CH50 was 36 mg/dL (low, normal: 42-91 mg/dL), C3 was 31 mg/dL (low, normal: 87-200 mg/dL), C4 was less than 8 mg/dL (low, normal: 19-52 mg/dL), ANA was 1:1280, anti-double-stranded (anti-DS) DNA antibody was not detected, fluorescent anti-nucleic acid antibody (ANA) was positive.