Coccidioides complement fixation is a blood test that looks for antibodies to the fungus Coccidioides immitis. This fungus causes the disease coccidioidomycosis.
Coccidioides antibody test
How the test is performed
A blood sample is needed. For information on how this is done, see: Venipuncture
The blood sample is sent to a lab. The health care provider looks at the clear liquid part of the blood, called serum, to see if there are antibodies to Coccidioides immitis.
How to prepare for the test
There is no special preparation for the test.
How the test will feel
When 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
This test is used to detect infection with the fungus that causes coccidioidomycosis. This condition can cause lung or widespread (disseminated) infection.
A normal result means no Coccidioides immitis antibodies are detected in the blood sample.
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean
Abnormal results mean that Coccidioides immitis antibodies are present. This can mean that you have a current or past infection.
The test may be repeated after several weeks to detect a rise in titer (antibody concentration), which confirms an active infection.
In general, the worse the infection, the higher the titer, except in people with a weakened immune system.
There can be false positive tests in patients with other fungal diseases such as histoplasmosis and blastomycosis, and false negative tests in people with single lung masses from coccidioidomycosis.
What the risks are
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other 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)
Galgiani JN. Coccidioides species. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases. 7th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2009:chap 266.
Galgiani JN. Coccidioidomycosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. Philadelphia, Pa: Saunders Elsevier; 2007:chap 354.
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