Alpha-1 antitrypsin is a laboratory test to measure the amount of alpha-1 antitrypsin (A1AT) in your blood.

Blood is typically 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.

There is no special preparation.

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.

This test is helpful in identifying a rare form of emphysema in adults and a rare form of liver disease (cirrhosis) in children and adults. If you do not have A1AT, certain digestive proteins (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 lower-than-normal levels of A1AT have one normal gene for A1AT, and one abnormal gene. Persons with two abnormal copies of the gene have more severe disease.

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

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

• Cirrhosis
• Emphysema or COPD
• Liver tumors
• Obstructive jaundice
• Portal hypertension

There is very little risk involved with having your blood taken. Veins and arteries vary in size from one patient 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 light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

Anthonisen N. Chronic obstructive pulmonary disease. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 88.