Aspergillosis precipitin

Definition

Aspergillosis precipitin is a laboratory test to detect antibodies in the blood resulting from exposure to the fungus aspergillus.

How the test is performed

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

For infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

Using immunologic testing techniques, the blood sample is examined for precipitin bands that form when aspergillus antibodies are present.

How to prepare for the test

There is no special preparation.

How the test will feel

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.

Why the test is performed

The test is performed when a fungal infection is suspected.

Normal Values

The normal test result is negative for aspergillus antibodies.

What abnormal results mean

Precipitins are often found in aspergillus "fungus ball" lung infections. About half of aspergillus hypersensitivity pneumonitis (allergic bronchopulmonary aspergillosis, also called ABPA) cases have positive precipitins. Invasive aspergillosis often does not have a positive preciptin test. It is a false-negative result. (Aspergillus is present, but the test is negative.)

What the risks are

The risks are associated with having blood drawn:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk anytime the skin is broken)
• Multiple punctures to locate veins

Special considerations

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.

Illustrations

Blood test

Page Content:

Aspergillus immunodiffusion test; Test for precipitating antibodies