Alpha-1 antitrypsin (AAT) deficiency is a clinically under-recognized genetic disorder that causes the defective production of alpha-1 antitrypsin protein. AAT protein protects the body from the neutrophil elastase enzyme, which is released from white blood cells to fight infection. This activity discusses the evaluation and management of AAT and highlights the role of the interprofessional team in managing and treating the disease to improve patient care.
This test measures the amount of alpha-1 antitrypsin (AAT) in the blood. AAT is a protein that is made in the liver. It helps protect your lungs from damage and diseases, such as emphysema and chronic obstructive pulmonary disease (COPD).
AAT is made by certain genes in your body. Genes are the basic units of heredity passed down from your parents. They carry information that determines your unique traits, such as height and eye color. Everyone inherits two copies of the gene that makes AAT, one from their father and one from their mother. If there is a mutation (change) in one or both copies of this gene, your body will make less AAT or AAT that doesn’t work as well as it should.
- 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 AAT gene, you may have lower than normal amounts of AAT, but mild or no symptoms of disease. People with one mutated gene are carriers of AAT deficiency. This means you don’t have the condition, but you could pass the mutated gene on to your children.
An AAT test can help show if you have the genetic mutation that puts you at risk for disease.
Other names: A1AT, AAT, alpha-1-antiprotease deficiency, α1-antitrypsin alpha-1 antitrypsin is a laboratory test to measure the amount of alpha-1 antitrypsin (A1AT) in your blood.
Why do I need this test?
The only way to find out whether you have this genetic disorder is to get tested.
Your healthcare provider may order this test if you have these problems:
-
Chronic wheezing
-
Asthma that can’t be controlled through aggressive treatment
-
Shortness of breath during mild exercise
-
Rapid heartbeat when you stand up
-
Vision problems
-
Chronic bronchitis
-
Bumpy or itchy skin
-
Chronic obstructive pulmonary disease (COPD)
-
Emphysema, a serious, progressive lung disease that causes breathing problems
-
Bronchiectasis, a lung problem that causes chronic dilation of the airways
-
Blood in your vomit
-
Swelling in your abdomen or legs
-
Unexplained liver problems, especially if they appear in childhood
-
Unintentional weight loss
Infants who have yellow skin, a sign of jaundice, may also be tested.
Your healthcare provider may also recommend the test if someone in your family has a history of the above conditions.
How the Test will Feel
When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away.
What other tests might I have along with this test?
Your healthcare provider may recommend other tests to rule out other conditions:
-
Pulmonary function testing. A series of tests to see how well your lungs work.
-
Chest radiography. X-ray of your lungs.
-
HRCT (high-resolution CT) and densitometry. More detailed X-rays of your lungs and tests to measure any lung and liver damage.
-
Liver function tests. A series of blood tests to see how well your liver works.
-
Abdominal ultrasound. A test that uses sound waves to find evidence of liver damage.
-
Liver biopsy. A procedure that involves taking a tiny sample of your liver to look for disease.
Your healthcare provider may do a series of tests on the serum in your blood to find the damaged genes. These tests include:
-
Serum AAT concentrations. Tests on a blood sample to look for the AAT protein.
-
Serum protein electrophoresis with thin-layer isoelectric focusing. A more accurate test for the gene.
-
Genetic test. You may consider getting a genetic test before getting a blood test. The genetic test can be done with a blood sample or a swab from inside your mouth.
Why the Test is Performed
This test is helpful in identifying a rare form of emphysema in adults and a rare form of liver disease (cirrhosis) in children and adults caused by an A1AT deficiency. A1AT deficiency is passed down through families. The condition causes the liver to make too little of a protein that protects the lungs and liver from damage.
Everyone has two copies of the gene that makes A1AT. Most people with a lower-than-normal level of A1AT have one normal gene for A1AT and one abnormal gene. People with two abnormal copies of the gene have more severe diseases.
Why do I need an AAT test?
You may need an AAT test if you are under the age of 45, are not a smoker, and have symptoms of lung disease, including:
- Wheezing
- Shortness of breath
- Chronic cough
- Faster than normal heartbeat when you stand up
- Vision problems
- Asthma that doesn’t respond well to treatment
You may also get this test if you have a family history of AAT deficiency.
AAT deficiency in babies often affects the liver. So your baby may need an AAT test if his or her health care provider finds signs of liver disease. These include:
- Jaundice, a yellowing of the skin and eyes that lasts for more than a week or two
- An enlarged spleen
- Frequent itching
Normal Results
Normal value ranges may vary slightly among different laboratories. Talk to your health care provider about the meaning of your specific test results.
What do the results mean?
If your results show a lower than normal amount of AAT, it probably means you have one or two mutated AAT genes. The lower the level, the more likely it is you have two mutated genes and AAT deficiency.
If you are diagnosed with AAT deficiency, you can take steps to reduce your risk of disease. These include:
- 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.
- Following a healthy diet
- Getting regular exercise
- Seeing your health care provider regularly
- Taking medicines as prescribed by your provider
- Damage of the large airways in the lungs ( bronchiectasis )
- Scarring of the liver ( cirrhosis )
- Chronic obstructive pulmonary disease (COPD)
- Liver tumors
- Yellowing of the skin and eyes due to blocked bile flow ( obstructive jaundice )
- High blood pressure in the large vein leads to the liver (portal hypertension )
Risks
There is very little risk involved with having your blood taken. Veins and arteries vary in size from one person to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight, but may include:
- Excessive bleeding
- Fainting or feeling lightheaded
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Key points
-
All adults with chronic obstructive pulmonary disease, asthma with incompletely reversible airway obstruction or necrotizing panniculitis, as well as people of any age with unexplained liver disease, should be screened for alpha-1 antitrypsin deficiency.
-
Screening involves testing the serum alpha-1 antitrypsin level; the diagnosis must be confirmed by genotyping or phenotyping.
-
People with diagnosed alpha-1 antitrypsin deficiency should undergo full pulmonary function testing, chest radiography and liver enzyme and function testing.
-
Treatment of alpha-1 antitrypsin lung disease includes general treatment for chronic obstructive pulmonary disease and consideration of augmentation therapy.
CMAJ remains committed to notifying readers in a timely way about advisories and warnings pertaining to serious adverse drug events.
References
