Alpha-1 antitrypsin

Alternative names 
AAT or A1AT

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

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 or blood pressure cuff is placed around the upper arm to cause veins 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. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.

How to prepare for the test
There is no special preparation.

For infants and children:
The preparation a parent can provide for this or any test or procedure depends on the child’s age, interests, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child’s age:

How the test will feel
When the needle is inserted to draw blood, some people may feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

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 two copies of the gene that makes A1AT. Most people with the disease have one normal gene for A1AT, and only one 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.

What abnormal results mean

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

What the risks are

     
  • 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

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 others.

Johns Hopkins patient information

Last revised: December 5, 2012
by David A. Scott, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.