C3: 55–120 mg/dL; SI units: 0.55–1.2 g/L
C4: 20–50 mg/dL; SI units: 0.2–.05 g/L
. Red-top tube.
■ Commonly assessed components of the complement
system.
■ Increased levels associated with rheumatoid arthritis, some
cancers, and acute viral hepatitis.
■ Decreased levels associated with SLE, glomerulonephritis,
DIC, gram-negative sepsis.
