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Alternative namesThis is a blood test that measures complement activity or the concentration of complement components in serum.
How the test is performed
Blood is drawn from a vein, usually on the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and an elastic band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to fill with blood.
A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
How to prepare for the testThere is no special preparation.
For infants and children:
The preparation you can provide for this test depends on your child's age, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics:
How the test will feelWhen the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
Complement activity (CH50, CH100, terminal complement component, or individual complement proteins ) is measured to determine if complement is involved in the development of a number of diseases. Complement activity is also measured to monitor how severe a disease is or to determine if treatment is working.
For example, patients with active lupus erythematosus may have lower-than-normal levels of C3 and C4 , and the levels of these complement components may be monitored to gauge disease activity.
(This test may also be reported as mg/L = milligrams per liter.)
What abnormal results meanIncreased complement activity may be seen in:
What the risks are
Complement is a group of proteins involved in immunological and inflammatory responses. There are 9 major components of complement labeled C1 through C9.
The "complement cascade" is a series of reactions that take place in the blood. The cascade can be started in several ways, especially by antigen-antibody complexes. The end product of the cascade is called the "membrane attack unit" (also called the terminal complement component). This attack unit creates holes in the membranes of attacking bacteria, killing them.
CH50 or CH100 are tests for the activity of the complement system. Typically, other tests that are more specific for the suspected disease are performed first.
Update Date: 8/6/2003Megan E. B. Clowse, M.D., M.P.H., Division of Rheumatology, Johns Hopkins Hospital, Baltimore, MD. Review provided by VeriMed Healthcare Network.
Last updated: Tue, 06 Jan 2009 00:20:03 GMT