A blood sample is needed.

The sample is sent to a laboratory. There, it is examined for bands called precipitin that form when specific antibodies are present.

There is no special preparation for the test.

When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or bruising. This soon goes away.

The precipitin test is one of several tests that can be done to determine if you are infected with Coccidioides, which causes the disease coccidioidomycosis.

Antibodies are specialized proteins that defend the body against bacteria, viruses, and fungi. These and other foreign substances are called antigens. When you are exposed to antigens, your body produces antibodies.

The precipitin test helps check if the body has produced antibodies to a specific antigen, in this case, the Coccidioides fungus.

A normal result is when no precipitins are formed. This means the blood test did not detect the antibody to Coccidioides.

An abnormal (positive) result means the antibody to Coccidioides has been detected.

In this case, another test is done to confirm that you have an infection. Your health care provider can tell you more.

During the early stage of an illness, few antibodies may be detected. Antibody production increases during the course of an infection. For this reason, this test may be repeated several weeks after the first test.

There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood 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
• Multiple punctures to locate veins
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Coccidioidomycosis antibody test; Coccidioides blood test; Valley fever blood test

Brady RC. Coccidioidomycosis (Coccidioides species). In: Kliegman RM, St. Geme JW, Blum NJ, Shah SS, Tasker RC, Wilson KM, eds. Nelson Textbook of Pediatrics. 21st ed. Philadelphia, PA. Elsevier; 2020:chap 267.

Galgiani JN. Coccidioidomycosis (Coccidioides species). In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 265.

Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.