C3 and systemic lupus erythematosus: The mean C3 concentrations were 118.3 (114.2–122.4) mg/dL in SLE and 130.8 (126.2–135.4) mg/dL in non-SLE, which represented a reduction of 9.6% of mean C3 level in SLE (p = 8 × 10−5).