AAT - Alpha-1 Antitrypsin

Overview & Description

This test measures the amount of the protein alpha-1 antitrypsin (A1AT) in the bloodstream. A1AT is made by the liver and released into the blood. It blocks the action of certain enzymes that are released by dying cells. These enzymes can cause the breakdown of key proteins in the body.

Who is a candidate for the test?

This test is normally performed on people with a family history of emphysema. These individuals often have an inherited deficiency of A1AT. The test may may also done to diagnose swelling, severe infection or tissue or bone death.

How is the test performed?

In order to measure the amount of alpha-1 antitrypsin in the blood, a blood sample needs to be taken. It is usually obtained from a vein on the forearm or hand. The skin over the vein is first cleaned with an antiseptic. Next, a strong rubber tube, or "tourniquet", is wrapped around the upper arm. This enlarges the veins in the lower arm. A thin needle is inserted gently into a vein and the tourniquet is removed. Blood flows from the vein through the needle. It is collected in a syringe or vial and sent to the lab for testing. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

Preparation & Expectations

What is involved in preparation for the test?

A person should request specific preparation instructions from his or her healthcare provider.

Results and Values

What do the test results mean?

Normal levels of A1AT in serum range from 93 to 224 mg/dl (milligrams per deciliter) in blood. If special test called serum protein electrophoresis is performed on the drawn blood, levels will range from 0 to 3.1 gm/dl (grams per deciliter).

Increased levels of this protein can occur whenever there is inflammation of some kind in the body or the body is subjected to stress.

Lower levels of A1AT may indicate:

  • cirrhosis or other liver disease
  • chronic obstructive pulmonary disease such as emphysema
  • tumors or abnormal growths of the liver
  • obstructive jaundice. This is yellowing of the skin that occurs when there is a blockage in the liver.
  • portal hypertension. This is high pressure in the liver's circulatory system.
  • alpha-1-antitrypsin deficiency. This means that the body has a shortage of this enzyme.

    • Attribution

    Author:David T. Moran, MD
    Date Written:
    Editor:Slon, Stephanie, BA
    Edit Date:04/20/00
    Reviewer:Eileen McLaughlin, RN, BSN
    Date Reviewed:09/20/01

    Sources

    Mosby's Manual of Diagnostic and Laboratory Tests, Kathleen D. Pagana and Timothy J. Pagana