(Normal range: 10-40 mg/dL (0.1-0.4 g/L
Comment: Quantitation of C4 is used to detect individuals with congenital deficiency or those with autoimmune disease such as lupus erythematous (SLE), rheumatoid arthritis, serum sickness, certain glomerulonephritides, chronic hepatitis, cryoglobulinemia, immune complex disease, and hereditary angioedema. C4 levels are sensitive indicators of SLE and proliferative glomerulonephritis disease activity. C4 maybe increased with autoimmune hemolytic anemia
Sample: Serum, in ice