Coccidioides precipitin is blood test that looks for antibodies to the fungus Coccidioides immitis, which causes the disease coccidioidomycosis.

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.

Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

This test specifically looks for the antibodies in the clear liquid portion of the blood, which is called the serum. (This technique is calledserology.) An antibody defends the body against bacteria, viruses, fungus, or other foreign body. Certain cells tell the body to produce antibodies during an active infection.

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.

There is no special preparation for the test.

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

The test detects infection with the fungus Coccidioides immitis, which causes the disease coccidioidomycosis.

No precipitation is normal.

A complement fixation titer will be performed if the precipitin test is positive. A titer less than 1:16 usually indicates no infection. However titers of 1:2 or 1:4 have been seen in people with active infection. A titer greater than 1:16 usually indicates active infection.

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 light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

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Mandell GL, Bennett JE, Dolin R. Principles and Practice of Infectious Diseases. 5th ed. London, UK: Churchill Livingstone; 2000:2746-2755.

Galgiani JN, Ampel N, Blair JE, et al. Coccidioidomycosis. Clin Infect Dis. 2005;41:1217-23.