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Alpha-1 antitrypsin

Alpha-1 antitrypsin

Definition

Alpha-1 antitrypsin measures the amount of alpha-1 antitrypsin (A1AT) in your blood serum.

Alternative Names

AAT or A1AT

Why the Test is Performed

This test is helpful in identifying a rare form of emphysema in adults and a rare form of cirrhosis in children. In the absence of A1AT, certain digestive enzymes released by white blood cells may go unchecked and cause widespread damage in the lungs and liver.

Everyone has 2 copies of the gene that makes A1AT. Most people with the disease have 1 normal gene for A1AT, and only 1 abnormal gene. These people will have lower-than-normal levels of A1AT, but not as low as people who have 2 abnormal copies and generally more severe disease.

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.

In 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.

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.

Risks

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

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 others.

What Abnormal Results Mean

Lower-than-normal levels of A1AT may be associated with:

Review Date: 1/17/2007
Reviewed By: Frank A. Greco, M.D., Ph.D., Director, Biophysical Laboratory, The Lahey Clinic, Burlington, MA. Review provided by VeriMed Healthcare Network.
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