Lupus Site - a guide for lupus patients and their families

Complement activity (CH50, CH100, terminal complement component, or individual complement proteins) is measured to determine if complement is involved in the pathogenesis of a number of diseases. Complement activity is also measured to monitor severity of a disease or determine efficacy of treatment. Complement (which comes in over 20 varieties) is important in getting rid of bacteria. Deficiency of certain complement molecules [especially C2, C4] increases the risk of developing SLE; these deficiencies run in families, ie can be inherited. Patients with active lupus erythematosus may have depressed levels of C3 and C4, and these component levels may be followed as a rough index of disease activity.

Total hemolytic complement level: 41 to 90 hemolytic units
C1 esterase inhibitor level: 16 to 33 mg/dl (160 to 330 mg/L)
C3 levels: males: 88 to 252 mg/dl (880 to 2520 mg/L) females: 88 to 206 mg/dl (880 to 2060 mg/L)
C4 levels: males: 12 to 72 mg/dl (120 to 720 mg/L) females: 13 to 75 mg/dl (130 to 750 mg/L)
Note: mg/dl = milligrams per deciliter. (This test may also be reported as mg/L = milligrams per liter.)

A positive test means - If the levels of complement are low, it means the body is undergoing a severe immune reaction. Although lupus is one cause, there are many others.

A negative test means - Normal levels of complement mean that lupus inflammatory kidney disease is unlikely. However, other types of kidney disease can still occur.