The Alpha-1 Antitrypsin (AAT) test is a blood test that measures the levels of the AAT protein in the blood. AAT is a protein produced primarily by the liver, and is responsible for protecting the body from damage caused by enzymes called proteases. The AAT test is commonly used to screen for and diagnose alpha-1 antitrypsin deficiency, a genetic disorder that can cause lung and liver disease. People with alpha-1 antitrypsin deficiency have low levels of AAT in the blood, which can result in damage to the lungs and liver over time. The AAT test involves taking a small sample of blood, which is then analyzed in a laboratory to determine the levels of the protein. Depending on the results of the test, doctors may recommend additional diagnostic tests or treatments to address underlying conditions. Regular monitoring of AAT levels can also be used to track the progression of alpha-1 antitrypsin deficiency and evaluate the effectiveness of treatment.