Coccidioides complement fixation

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Coccidioides complement fixation is a blood test that looks for antibodies to the fungus Coccidioides immitis. This fungus causes the disease coccidioidomycosis.

Alternative Names

Coccidioides antibody test

How the Test is Performed

A blood sample is needed.

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. Afterward, there may be some throbbing.

Why the Test is Performed

This test is used to detect infection with the fungus that causes coccidioidomycosis or valley fever. This condition can cause lung or widespread (disseminated) infection.

Normal Results

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 recent 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 is the titer, except in people with a weakened immune system.

There can be false positive tests in people with other fungal diseases such as

and , and false negative tests in people with single lung masses from coccidioidomycosis.


Veins and arteries vary in size from one person 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. Coccidioidomycosis (Coccidioides species). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 267.

Iwen PC. Mycotic diseases. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 61.

Version Info

  • Last reviewed on 9/10/2015
  • Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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