What is alpha-1 antitrypsin test?

Alpha-1 antitrypsin (AAT) test is a test that measures the level of AAT, which is a type of protein in the blood that protects the lungs from damage caused by activated enzymes in blood. Related tests can also determine which of the abnormal forms of AAT a person has inherited.

The primary function of AAT is to help inactivate several enzymes, the most important of which is elastase. Elastase is an enzyme produced by white blood cells called neutrophils and is part of the body’s normal response to injury and inflammation. Elastase breaks down proteins so that they can be removed and recycled by the body. If its action is not regulated by AAT, elastase will also begin to break down and damage lung tissue.

Why is alpha-1 antitrypsin test performed?

There are a couple of reasons why the alpha-1 antitrypsin test may be done:

  • Alpha-1 antitrypsin (AAT) testing is used to help diagnose alpha-1 antitrypsin deficiency as the cause of early onset emphysema, especially when a person does not have obvious risk factors such as smoking or exposure to lung irritants such as dust and fumes.
  • Testing is also ordered to help diagnose the cause of persistent jaundice and other signs of liver dysfunction. This is done primarily in infants and young children but may be done in people of any age.

Three types of AAT tests are available. One or more of these may be used to evaluate an individual:

  • Alpha-1 antitrypsin measures the level of the protein AAT in blood.
  • Alpha-1 antitrypsin phenotype testing evaluates the amount and type of AAT being produced and compares it to normal patterns.
  • Alpha-1 antitrypsin genotype testing (DNA testing) can be used to establish which SERPINA1 gene alleles are present, including the normal wild type M allele or variant alleles. This test does not identify every variant, but it will detect the most common ones (S and Z) as well as variants that may be common in a particular geographical area or family. Once the affected person’s SERPINA1 gene alleles have been identified, other family members may be tested to establish their own risk of developing emphysema and/or liver involvement as well as the likelihood that their children might inherit the disease.


What should I know before receiving alpha-1 antitrypsin test?

Some people will be ordered Alpha-1 antitrypsin test when:


  • An infant has jaundice that lasts for more than a week or two, an enlarged spleen, fluid accumulation in the abdomen (ascites), persistent itching (pruritus), and other signs of liver injury.
  • A person younger than 40 years of age develops wheezing, a chronic cough or bronchitis, is short of breath after exertion, and/or shows other signs of emphysema. This is especially true when the person is not a smoker, has not been exposed to known lung irritants, and when the lung damage appears to be located low in the lungs.
  • Someone has a close relative with alpha-1 antitrypsin deficiency.
  • An individual has an affected family member and wants to know the likelihood of having an affected child.

AAT is an acute phase reactant. This means that it will be elevated in acute and chronic inflammatory conditions, infections, and with some cancers. The increase of AAT levels may also be seen with oral contraceptive use, pregnancy, and stress. These temporary or chronic AAT increases may cause levels to appear normal in people with mild to moderate AAT deficiency.

AAT levels may be decreased in neonatal respiratory distress syndrome and in conditions that cause a decrease in serum proteins, such as kidney disease, malnutrition, and some cancers.


How to prepare for alpha-1 antitrypsin test?

It is advisable that there are a great number of things that need preparing before the test, including:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Hook a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Put a gauze pad or cotton ball over the needle site as the needle is removed.
  • Put pressure on the site and then put on a bandage.

What happens during alpha-1 antitrypsin test?

During this test, you may undergo:

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. Therefore, it may feel tight and uncomfortable. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

What happens after alpha-1 antitrypsin test?

Very little chance of a problem from having a blood sample taken from a vein can occur.

Firstly, you may get a small bruise at the site. However, you can lower the chance of bruising by keeping pressure on the site for several minutes.

In some rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. You should use a warm compress several times a day to solve this situation

Moreover, ongoing bleeding can be a problem for some patients with bleeding disorders. Some medications such as aspirin, warfarin (Coumadin), and other blood-thinning medicines are able to make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood sample is taken.

If you have any questions about the alpha-1 antitrypsin test, please consult with your doctor to better understand your instructions.

Explanation of results

What do my results mean?

  • AAT level

A low level of AAT in blood indicates that the person tested may have alpha-1 antitrypsin deficiency. The lower the level of AAT is, the greater the risk of developing emphysema.

  • Phenotype test

In people with an abnormal form of AAT, the risk of developing disease depends on how much is produced and which variant is present. A variant with very low activity may lead to both emphysema (because it does not protect the lungs) and liver disease (because of the buildup of abnormal AAT inside liver cells).

  • Genotype test

Most people have two copies of the normal wild type (MM) gene and produce sufficient AAT.

When DNA testing indicates the presence of one or two abnormal copies of the SERPINA1 gene, less AAT and/or abnormal AAT will be produced. The degree of AAT deficiency and the degree of lung and/or liver damage can vary greatly.

Please discuss with your doctor any questions you may have about your test results.

Hello Health Group does not provide medical advice, diagnosis or treatment.


Review Date: September 8, 2017 | Last Modified: September 8, 2017

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