Alpha-1 Antitrypsin Testing
- Also Known As:
- 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
Test Quick Guide
Alpha-1 antitrypsin (AAT) testing is performed to detect a deficiency of the AAT protein. The AAT protein is involved in protecting the lungs and liver from damage.
AAT deficiency is an inherited disorder that heightens the risk of chronic obstructive pulmonary disorder (COPD), a serious lung condition that makes it hard to breathe. AAT deficiency can also contribute to liver and skin problems.
Several types of tests can be used to detect an AAT deficiency. Testing can measure AAT levels and check for evidence of the underlying genetic mutations that cause AAT deficiency.
About the Test
Purpose of the test
The purpose of alpha-1 antitrypsin testing is to look for indications of an AAT deficiency. AAT tests can be used for diagnosis, screening, and treatment planning.
Diagnosis is the process of identifying the cause after a person has already shown symptoms of a health problem. Diagnostic testing may be performed to detect AAT deficiency in people who have symptoms that could be related to this disorder.
Screening is checking for a health problem before it has caused any symptoms. Because AAT deficiency is inherited, some family members of people with AAT deficiency may be tested even if they have not experienced any signs of the condition.
Treatment planning is the way a doctor determines the optimal treatment for a patient. In some cases, therapy for lung problems may be influenced by testing for AAT deficiency.
What is alpha-1 antitrypsin deficiency?
Alpha-1 antitrypsin deficiency is an inherited condition that is associated with a heightened risk of lung and liver disease. AAT deficiency is relatively rare, but research indicates that it often goes undiagnosed.
The AAT protein helps protect tissues in certain parts of the body from damage. People who don’t have enough AAT are more likely to develop potentially serious health conditions including:
- Chronic obstructive pulmonary disorder (COPD): COPD is a lung disorder marked by impaired breathing. Emphysema is a type of COPD triggered by damage to the lungs. COPD is the most common complication of AAT deficiency, and AAT deficiency is estimated to cause up to 3% of cases of emphysema in the United States. People with AAT are more likely to have emphysema if they also smoke or are exposed to chemicals or dusts that irritate the lungs.
- Liver diseases: Some people with an AAT deficiency experience damage to the liver. Examples of liver diseases that can be related to AAT deficiency include hepatitis, which is inflammation of the liver, and cirrhosis, which is scarring of the liver. AAT deficiency can also heighten the risk of primary liver cancer.
- Panniculitis: While much less common, an AAT deficiency can cause panniculitis, which is a condition involving red nodules on the skin that feel painful and hot. These nodules most often occur around the buttocks, thigh, or abdomen.
Some research indicates that an AAT deficiency may be related to other kinds of health problems, but links to other conditions have not been clearly proven.
What does the test measure?
Alpha-1 antitrypsin is a type of protein. Specifically, it is a protease inhibitor, which means that it helps block the effects of certain substances that can inflict damage on cells of the lungs and liver.
There are several kinds of AAT tests. Tests can measure blood levels of the AAT protein and look for evidence of AAT proteins that are abnormal or not functioning correctly. In addition, testing can look for the inherited genetic variations that cause AAT deficiency.
There are four main categories of AAT deficiency testing. Each type of testing measures something different about AAT:
- AAT blood level test: This test measures the amount of AAT protein found in a sample of blood to see if AAT levels are abnormal.
- AAT phenotype test: This test checks for the presence of abnormal forms of the AAT protein in the blood. A technical name for this type of testing is isoelectric focusing.
- AAT genotyping: This test looks for specific genetic changes in your DNA that are linked to an AAT deficiency. AAT genotyping can be done with a blood sample or by taking a swab from the inside of your cheek.
- DNA sequencing: This type of testing creates a more complete picture of the section of your DNA that provides the code for the AAT protein. It enables the identification of uncommon genetic variants that may not be found on an AAT genotyping test.
Depending on the circumstances, a doctor may prescribe one or more of these tests to determine whether a person has an inherited condition affecting the alpha-1 antitrypsin protein. Multiple tests may be prescribed at the same time, or they can be done in a sequence of initial testing with follow-up tests to confirm the first result.
When should I get an alpha-1 antitrypsin test?
Alpha-1 antitrypsin testing may be performed under several different circumstances.
For diagnosis, testing is only done when you have signs or symptoms that could be explained by an underlying AAT deficiency. For example, AAT testing is frequently performed in people who have tests that show reductions in their ability to exhale air out of the lungs, which is common in people with emphysema and COPD.
Other signs and symptoms that may warrant diagnostic AAT testing to be recommended include:
- Emphysema that begins at age 45 or earlier, occurs in nonsmokers, or has certain anatomic features related to how it affects the lungs
- A family history of emphysema or liver disease
- Asthma that starts during adulthood, especially if it doesn’t get better with treatment
- Bronchiectasis, which is enlargement of the tubes that carry air to the lungs
- Panniculitis, which involves painful nodules on the skin
- Liver disease without a known cause
In infants, AAT testing may be advised if there are signs or symptoms of abnormal liver function.
AAT testing may be considered if you have a first-degree family member who has been diagnosed with AAT deficiency. In most cases, you will be offered genetic counseling beforehand to discuss the benefits and downsides of AAT tests in your case.
AAT deficiency is more common in some geographic areas and populations groups. Prevalence of the condition is highest in people of European descent. The decision about whether to conduct AAT testing may be affected by the extent of AAT deficiency in your specific area or ancestry group.
It is important to talk with a doctor who can most concretely address whether you have any potential signs of AAT deficiency and whether AAT testing is appropriate in your situation.
Finding an Alpha-1 Antitrypsin Test
How to get tested
AAT testing is usually prescribed by a doctor who selects the specific kind of testing to perform. Some AAT tests require a blood sample that can be taken in a medical office, laboratory, or hospital. For other tests, the sample is taken by swabbing the inside of your mouth.
Can I take the test at home?
Some at-home options are available for certain types of alpha-1 antitrypsin testing. The main types of at-home AAT tests are focused on finding genetic mutations that are linked to AAT deficiency.
In one version of this testing, you provide a blood sample by pricking your finger and placing a drop of blood on special test paper. This test paper is then sent to a laboratory in a prepaid envelope. The laboratory conducts AAT genotype testing, and the results are provided confidentially through the mail.
Another type of AAT test that you can order and have delivered to your home analyzes a sample taken from your mouth. These test kits, which use a cheek swab to check for genetic changes tied to AAT deficiency, must then be taken to your doctor’s office where the testing can be performed.
AAT deficiency testing may also be done as part of broader DNA testing that is available from companies that offer at-home DNA ancestry testing. This testing, like the other approaches, looks for genetic variations in the part of your DNA that regulates AAT.
Your doctor is in the best position to help you determine whether at-home AAT testing is right for you. If you receive abnormal results on an at-home test, your doctor will likely order follow-up testing to confirm the results.
How much does the test cost?
The cost of alpha-1 antitrypsin testing depends on multiple factors including which type or types of testing is conducted, where the test is performed, and whether you have health insurance.
Charges for AAT testing can include fees for office visits, the blood draw, and laboratory analysis of your test sample. Insurance may provide coverage for some or all of these charges, but you may be required to pay for deductibles or copayments. For detailed information about the costs of AAT testing, talk with your doctor’s office and your health insurance provider.
If you do not have health insurance, check with your doctor or a hospital administrator about expected charges and whether any programs are available to reduce testing costs for people who are uninsured. In addition, some organizations have ongoing research studies that include free AAT deficiency testing.
Taking a Alpha-1 Antitrypsin Test
For some AAT tests, a blood sample can be taken from your fingertip. After disinfecting your fingertip, the nurse or phlebotomist pricks your finger with a tiny needle to collect a few drops of blood. Fingerstick blood tests are very quick and involve only a brief and minor sting.
If you are having an AAT genotyping test with a cheek swab sample, a health care professional will use a special swab that is rubbed for a few seconds along the inside of your cheek. This test is usually painless.
AAT testing is performed by a laboratory after being prescribed by a doctor. The sample required depends on the type of AAT testing being conducted.
AAT blood levels tests and AAT phenotyping require a blood sample. In most cases, the blood sample is taken from a vein in your arm during a routine procedure done in a doctor’s office, hospital, or laboratory clinic. Sometimes the sample can be provided with a drop of blood from your fingertip.
AAT genotyping can be done with a blood sample or a cheek swab sample collected by a health care professional.
Before the test
There are not usually any specific preparations required for AAT tests. Check with your doctor to confirm whether there are any pretest instructions to follow.
If you are having an AAT test that uses a cheek swab, you may be requested to rinse out your mouth prior to testing.
During the test
Many AAT tests are done with a needle blood draw. In this routine procedure, a trained practitioner, such as a nurse or phlebotomist, starts by tying an elastic band around your upper arm to increase blood flow in your veins. They disinfect an area of skin, usually near the inside of your elbow, and then insert a needle into the vein to withdraw a vial of blood.
A normal blood draw lasts less than a few minutes. You may experience a slight sting or other minor pain during the test.
After the test
Once a needle blood draw is finished, a cotton swab and bandage are frequently applied to the puncture site to apply pressure and prevent further bleeding. There may be some bruising or soreness in your arm, but you can return to normal activities once the test is complete.
After a fingerstick blood test, a bandage may be placed on your finger if necessary to keep it from bleeding. There are no post-test restrictions after this kind of blood test.
A cheek swab test does not cause any side effects, and there are no activity restrictions once the test is over.
Alpha-1 Antitrypsin Test Results
Receiving test results
Many AAT test results are available within a few business days, but the exact timeline depends on the type of testing that is done. Because different kinds of laboratory analysis can be performed, you should check with your doctor about the normal timeline for results.
The doctor may contact you by phone or schedule an appointment to discuss your AAT test results. Complete test reports may also be available by mail or through a secure online health portal.
Interpreting test results
The interpretation of AAT test results varies significantly based on which test or tests were performed and the methods that the laboratory used to analyze your test sample.
AAT deficiency is not diagnosed on the basis of one test alone. Instead, an AAT deficiency diagnosis requires a test result indicating low blood levels of AAT and a confirmatory test showing abnormal results on either an AAT phenotyping or genotyping test.
AAT blood levels can be measured in different ways and may be reported in milligrams per deciliter (mg/dL) of blood or in micromoles per liter (µM/L). It is important to pay careful attention to the unit of measurement when reviewing your test results.
Your test result will then be compared to its reference range. This reference range reflects what that laboratory considers to be a normal AAT level based on its measurement techniques. Looking at this specific reference range is critical because normal levels are strongly influenced by the laboratory’s methods.
If your blood test shows low levels of the AAT protein, additional tests may be performed to assess the AAT phenotype or genotype. These tests can show whether there are abnormalities in the activity of the AAT protein or in the genetic code that is responsible for AAT protein function.
If you have low AAT levels in the blood and abnormal results on an AAT phenotype or genotype test, you may be diagnosed with AAT deficiency. People with AAT deficiency can have an elevated risk of lung and liver disease. However, not all people with AAT deficiency develop these health problems. There are numerous subtypes of AAT deficiency based on the particular genetic changes that affect AAT function.
AAT test results are used to determine whether a person has AAT deficiency, which subtype of AAT deficiency they have, and what that deficiency means for their health. For this reason, you should always review your test results with a doctor who can explain how those results can be interpreted in the context of your personal situation.
Are test results accurate?
Testing for diagnosing alpha-1 antitrypsin deficiency is generally accurate. Although no single type of AAT test is perfectly accurate, the combination of test methods enables AAT deficiency to be effectively identified with high levels of confidence.
Do I need follow-up tests?
If you have an initial test that measures only the blood levels of AAT, you may need further testing. Most often, this follow-up testing is with an AAT genotyping test that looks for genetic variants that cause AAT deficiency. However, many doctors prescribe AAT blood level tests and AAT genotyping tests at the same time.
If testing shows that you have an AAT deficiency, your doctor may recommend additional testing to evaluate your lung and liver function. For example, many patients with AAT deficiency have pulmonary function testing, imaging tests like a CT scan of the chest, and/or a liver panel test.
Questions for your doctor about alpha-1 antitrypsin test results
When you review your AAT test with your doctor, some of these questions may help you to understand your results and what they mean for your health:
- Which type of AAT test did I have?
- Did the test show signs of an AAT deficiency?
- Are any other tests needed to determine if I have an AAT deficiency?
- Do you recommend any other types of follow-up testing?
- If I am AAT deficient, should I inform any family members about this diagnosis?
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