This test is used to detect the presence of antibodies to Coxiella burnetii (C. burnetii) bacteria in the blood. This highly infectious bacteria causes Q fever.

The test is performed to detect Q fever.

Antibodies defend the body against bacteria, viruses, fungi, and other foreign substances, called antigens. Certain cells cause the body to produce antibodies during an active infection.

When you first become sick, few antibodies may be detected. Antibody production increases during the course of an infection. Antibody tests are often repeated several weeks after the first test is done, so that a comparison can be made to the first test. A rising level of antibody to a specific infectious agent tells the health care provider that you have an active infection.

The complement fixation test looks to see if the body has produced antibodies to a specific antigen -- in this case, the C.burnetii bacteria. If the antibodies are present, they stick, or "fix" themselves, to the antigen, that's why the test is called "fixation."

The test specifically looks for the antibodies to C. burnetii in the clear liquid portion of the blood called the serum. (The general term for such a technique is called serology.) If you have consistently high levels of antibodies to C. Burnetii, this indicates chronic Q fever.

No special preparation is necessary for this test.

A needle is inserted to draw blood. You may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.