CSF coccidioides complement fixation

Definition

CSF coccidioides complement fixation looks for antibodies to the fungus Coccidioides immitis in the cerebrospinal (CSF) fluid, the fluid surrounding the brain and spine.

Alternative Names

Coccidioides antibody test - spinal fluid

How the test is performed

Complement fixation is a specific laboratory technique that looks to see if the body has produced antibodies to a specific foreign substance (antigen) -- in this case Coccidioides immitis. If the antibodies are present, they stick, or "fix" themselves, to the antigen. That's why the test is called "fixation."

The spinal fluid needed to perform this test is usually obtained by lumbar puncture (spinal tap).

How to prepare for the test

A consent form must be signed. You will need to remain in the hospital for about 8 hours afterwards, and you should remain lying flat.

How the test will feel

See: Lumbar puncture

Why the test is performed

Complement fixation is the most sensitive test for the fungus Coccidioides immitis.

Normal Values

The absence of fungus (a negative test) is normal.

What abnormal results mean

If the test is positive for fungus, the results indicate an active infection in the central nervous system. (See: Disseminated coccidioidomycosis ).

What the risks are

See: Lumbar puncture

Special considerations

In some cases, this test may be done as a blood test. See also: Coccidioides complement fixation.

In the initial stage of an illness, few antibodies may be detected. Antibody production increases during the course of an infection. For this reason, such tests are often repeated several weeks after the first test is done.

Note: While an abnormal result on the spinal fluid test specifically means that the central nervous system is infected, an abnormal result on the blood test does not pinpoint the exact area of infection. It only means that there is a coccidioides infection somewhere in the body.

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References

Galgiani JN. Coccidioidomycosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007: chap 354.