This test is used to detect hereditary decreases in the production of alpha-1 antitrypsin (AAT). AAT is responsible for inactivating endoproteases (protein catabolic enzymes). Sparse levels of AAT can be a factor in chronic obstructive lung disease and liver disease. Raised levels can also be an indication of inflammatory states (eg, rheumatoid arthritis, bacterial infection, vasculitis, neoplasia). An 8 to 12 hour fast is required for this blood test. However, drink plenty of water and take medications as prescribed.