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Alpha-1 Antitrypsin Testing

What is alpha-1 antitrypsin (AAT) testing?

Alpha-1 antitrypsin (AAT) testing uses a sample of blood or a cheek swab to diagnose a condition called alpha-1 antitrypsin deficiency (AAT deficiency). This condition is sometimes known as "alpha-." or AATD. If you have AAT deficiency, your body doesn't make enough AAT.

AAT is made by your liver. It helps protect your lungs from inflammation and irritating substances you might breathe in, such as smoke. If your liver doesn't make enough AAT, your lungs may be more easily damaged from smoking, pollution, or dust from the environment. This can lead to a serious lung condition called chronic obstructive pulmonary disease (COPD). AAT deficiency may also cause a liver disease called cirrhosis. This is more common in children who have AAT deficiency.

AAT deficiency is a genetic disorder. That means it's caused by changes in your genes, which may also be called gene variants or mutations.

Genes carry information that controls what you look like and how your body works. AAT deficiency is caused by changes in the SERPINA1 gene, which carries instructions for making the AAT protein. These gene changes are inherited from your parents, so AAT deficiency tends to run in families.

  • If you have two mutated copies of the gene, it means you have a condition called AAT deficiency. People with this disorder have a higher risk of getting lung disease or liver damage before the age of 45.
  • If you have one mutated copy of the gene, you are a carrier of AAT deficiency. In these cases, this means you are at slightly higher risk of developing lung disease, especially if you other risk factors, such as being a smoker. You could pass the mutated gene on to your children.

There are a few gene changes that cause AAT deficiency. These gene changes can:

  • Decrease the amount of AAT protein your liver makes.
  • Prevent your liver from making any AAT.
  • Affect the shape of the AAT protein so that it can't move out of your liver to protect your lungs. Over time, AAT builds up in your liver and causes damage.

A genetic test can help you find out whether you have the gene change that increases your risk for lung and liver disease.

There are three types of testing to help diagnose AAT deficiency:

  • The AAT blood level test measures the amount of protein found in your blood to see if your AAT levels are abnormal.
    • If your AAT levels are abnormally low, a genetic test (either a genotype test or a phenotype test) is needed to confirm a diagnosis of AAT deficiency.
  • The genotype test looks for the more common types of gene changes that can cause AAT deficiency.
  • The phenotype test checks for changes in the AAT protein that change how it would normally work.

Other names: A1AT, AAT, alpha-1-antiprotease deficiency, α1-antitrypsin, serum AAT test, AAT phenotyping, AAT genotyping, AAT deficiency test, AAT DNA sequencing test, AAT isoelectric focusing test, A1AT test, AATD test, alpha-1 protease inhibitor deficiency test

What is it used for?

There are three main uses for AAT testing:

  • To diagnose or rule out AAT deficiency in people who have symptoms of lung and/or liver disease that may be caused by AAT deficiency
  • To screen people who don't have symptoms, but have family members with AAT deficiency
  • To guide treatment choices for lung disease that may be caused by AAT deficiency

Why do I need AAT testing?

Diagnostic AAT testing may be recommended if you have the signs and symptoms of AAT deficiency or if you have conditions that could be caused by AAT deficiency.

Signs and symptoms of AAT deficiency may include:

Conditions that could be caused by AAT deficiency can include:

  • COPD (chronic obstructive pulmonary disease)
  • Repeated respiratory infections, such as colds and bronchitis
  • Asthma that doesn't respond well to treatment
  • Panniculitis, a skin condition that causes hardened skin with painful lumps or patches
  • Liver disease without a known cause
  • Jaundice (yellowing of the skin and eyes)

You may also get this test if you have a family history of AAT deficiency, emphysema, or unexplained cirrhosis.

AAT deficiency in babies often affects the liver. Your baby may need AAT testing if he or she has signs of liver disease such as jaundice or abnormal liver enzyme tests.

What happens during AAT testing?

AAT blood testing may involve a blood test with blood from your arm or a finger prick. Some genetics tests involve a cheek swab.

For a blood test from your arm, a health care professional will take the blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

For a finger prick test, a health care professional will prick your fingertip to obtain a small amount of blood.

For a cheek swab, a health care professional will wipe the inside of your cheek with a small tool to remove some cells. You may have the option of doing it yourself.

Will I need to do anything to prepare for the test?

You don't need any special preparations for an AAT test.

Are there any risks to the test?

There is very little physical risk to a blood test. If the blood was taken from your arm, you may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

There are no risks to having a cheek swab.

What do the results mean?

If your AAT blood levels are low, it may mean you have AAT deficiency. To confirm the diagnosis, you'll need a genotype or phenotype test.

If that testing shows that you have AAT deficiency, your provider may recommend additional testing to evaluate your lung and liver function.

There is no cure for AAT deficiency. But treatments can help prevent your condition from getting worse. Your exact treatment will depend on your symptoms.

You can also take steps to stay as healthy as possible, including:

  • Not smoking. If you are a smoker, quit smoking. If you don't smoke, don't start. Smoking is the leading risk factor for life-threatening lung disease in people with AAT deficiency.
  • Not drinking alcohol. Alcohol can damage your liver.
  • Following a healthy diet.
  • Getting regular exercise.
  • Seeing your provider regularly.
  • Taking medicines as prescribed by your provider.

If you have questions about your results, talk to your provider.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about AAT testing?

If you're thinking about having AAT testing or have received abnormal results, it may be helpful to speak with a genetic counselor. A genetic counselor is a specially trained professional in genetics and genetic testing. A counselor can help you understand the risks and benefits of testing for you and your family. After testing, a counselor can help you understand your results. If you have AAT deficiency, the counselor can provide information on the condition, including your risk of passing the disease to your children.


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The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.