Serum alpha 1 -antitrypsin (AAT) determinations are obtained in patients with a family history of emphysema, because there is a familial tendency for a deficiency of this anti-enzyme. Deficient or absent serum levels of this enzyme can cause the early onset of disabling emphysema. A similar deficiency in AAT is seen in children with cirrhosis and other liver diseases. AAT is also an acute-phase reactant protein that is elevated in the presence of inflammation, infection, or malignancy. It is not specific regarding the source of the inflammatory process.