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alpha-1 antitrypsin

Alternative Names 
alpha-1 antitrypsin, AAT

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 also be 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 laboratory for testing. After the needle is withdrawn, the puncture site is covered for a short time to prevent bleeding.

What is involved in preparation for the test? 
A person should request specific preparation instructions from his or her doctor.

What do the test results mean? 
Normal ranges of Alpha-1-antitrypsin are:
  • male adults, 0.7 - 2.3 g/L (grams per Litre)
  • female adults, 0.9 - 2.7 g/L
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
  • tumours 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.
Author: David T. Moran, MD
Reviewer: eknowhow Medical Review Panel
Editor: Dr John Hearne
Last Updated: 6/06/2005
Potential conflict of interest information for reviewers available on request

This website and article is not a substitute for independent professional advice. Nothing contained in this website is intended to be used as medical advice and it is not intended to be used to diagnose, treat, cure or prevent any disease, nor should it be used for therapeutic purposes or as a substitute for your own health professional's advice.  All Health and any associated parties do not accept any liability for any injury, loss or damage incurred by use of or reliance on the information.


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