Type of test Blood
Normal findings
 85-213 mg/dL or 0.85-2.13 g/L (SI units)
 Negative for S or Z phenotype
Test explanation and related physiology
 Serum alpha1-antitrypsin (AAT) levels should be obtained when an individual has a family history of early emphysema. AAT mutated genes can be associated with reduced levels of this enzyme. Patients with mutated AAT genes develop severe, disabling lower lung emphysema in the third and fourth decades of life. A similar deficiency is seen in children with cirrhosis and other liver diseases. The severity of these diseases is determined by the ATT phenotype.
Routine serum protein electrophoresis  is a good screening test for AAT deficiency because AAT accounts for about 90% of the protein in the alpha1-globulin region. Quantitative serum levels indicate deficiency. If levels are low, ATT phenotyping can be performed. The three major alleles determined by phenotyping are: M (full functioning, normal allele), S (associated with reduced levels of protein), and Z (disease-causing mutation associated with liver disease and premature emphysema). The S and Z alleles account for the majority of the abnormal alleles detected in affected patients.
Inherited AAT deficiency is associated with symptoms earlier in life than acquired AAT deficiency. Inherited AAT is also commonly associated with liver and biliary disease. Individuals of the heterozygous state have diminished or low normal serum levels of AAT. Approximately 5% to 14% of the adult population is in the heterozygous state and is considered to be at increased risk for the development of emphysema. Homozygous individuals have severe pulmonary and liver disease very early in life. AAT phenotyping is particularly helpful when blood AAT levels are suggestive but not definitive.
Deficiencies of AAT can also be acquired. Acquired deficiencies of AAT can occur in patients with protein deficiency syndromes (e.g., malnutrition, liver disease, nephrotic syndrome, and neonatal respiratory distress syndrome).
AAT is also an acute-phase reactant that is elevated in the face of inflammation, infection, or malignancy. It is not specific as to the source of the inflammatory process.
Interfering factors
 • Serum levels of AAT increase during pregnancy or inflammatory diseases.
* Drugs that may cause increased levels include oral contraceptives.
 Procedure and patient care
 • See inside front cover for Routine Blood Testing.
 • Fasting: no (verify with laboratory)
 • Blood tube commonly used: red
*  If the results show the patient is at risk for developing emphysema, begin patient teaching. Include such factors as avoidance of smoking, infection, and inhaled irritants; proper nutrition; adequate hydration; and education about the dis ease process of emphysema.
Abnormal findings
 Increased levels
- Acute inflammatory disorders
- Chronic inflammatory disorders
- Stress
- Infection
- Thyroid infections
Decreased levels
 Early onset of emphysema (in adults)
- Neonatal respiratory distress syndrome
- Cirrhosis (in children)
- Low serum proteins (e.g., nephrotic syndrome, malnutrition, end-stage cancer, protein-losing enteropathy)