Alpha-1 Antitrypsin 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.;

Why this test is done

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:

• Wheezing
• Shortness of breath after exercise
• Chronic cough with phlegm (mucus)
• Chest pain
• Fatigue
• Faster-than-normal heartbeat when you stand up
• Vision problems

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.

How to prepare

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

Sample type

Blood

Other names for this test

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