LAB TEST
Complement
Complement is a blood test that measures the activity of certain proteins in the liquid portion of your blood. The complement system is a group of nearly 60 proteins that are in blood plasma or on the surface of some cells. The proteins work with your immune system and play a role to protect the body from infections, and to remove dead cells and foreign material. Rarely, people may inherit deficiency of some complement proteins. These people are prone to certain infections or autoimmune disorders. There are nine major complement proteins. They are labeled C1 through C9. This article describes the test that measures total complement activity.
How the Test is Performed
A blood sample is needed. This is most often taken through a vein. The procedure is called a venipuncture .
How to Prepare for the Test
There is no special preparation.
How the Test will Feel
When the needle is inserted to draw blood, some people feel slight pain. Others may feel only a prick or sting. Afterward, there may be some throbbing.
Why the Test is Performed
Total complement activity (CH50, CH100) looks at the overall activity of the complement system. In most cases, other tests that are more specific for the suspected disease are done first. C3 and C4 are the complement components measured most often. A complement test may be used to monitor people with an autoimmune…
Normal Results
The normal results for this test are: Total blood complement level: 41 to 90 hemolytic units C1 level: 14.9 to 22.1 mg/dL C3 levels: 88 to 201 mg/dL C4 levels: 15 to 45 mg/dL Note: mg/dL = milligrams per deciliter. Note: Normal value ranges may vary slightly among different laboratories. Talk to your health care…
What Abnormal Results Mean
Increased complement activity may be seen in: Cancer Certain infections Ulcerative colitis Decreased complement activity may be seen in: Cirrhosis Glomerulonephritis Hereditary angioedema Hepatitis Kidney transplant rejection Lupus nephritis Malnutrition Systemic lupus erythematosus Rare inherited complement…
Risks
Risks associated with having blood drawn are slight, but may include: Excessive bleeding Fainting or feeling lightheaded Hematoma (blood accumulating under the skin) Infection (a slight risk any time the skin is broken)
Considerations
The "complement cascade" is a series of reactions that take place in the blood. The cascade activates the complement proteins. The result is an attack unit that creates holes in the membrane of bacteria, killing them.
References
Bean KV, Massey D, Gupta G. Mediators of inflammation: complement. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 47. Ram S. Complement and deficiencies. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and…
This is a summary. Read the full article at www.ucsfbenioffchildrens.org (reviewed 25/01/2023).
This page is general information and is not medical advice. It does not replace a registered doctor, and it is not a prescription or a recommendation to use any medicine or test. Prices are listed prices and may change. Always follow the advice of your doctor or pharmacist.