AAT - Clinical: Alpha-1-Antitrypsin, Serum

Test Catalog

Test Name

Test ID: AAT    
Alpha-1-Antitrypsin, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Workup of individuals with suspected disorders such as familial chronic obstructive lung disease


Diagnosis of alpha-1-antitrypsin deficiency

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Alpha-1-Antitrypsin-A Comprehensive Testing Algorithm in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Alpha-1-antitrypsin (A1A) is the most abundant serum protease inhibitor and inhibits trypsin and elastin, as well as several other proteases. The release of proteolytic enzymes from plasma onto organ surfaces and into tissue spaces results in tissue damage unless inhibitors are present. Congenital deficiency of A1A is associated with the development of emphysema at an unusually early age and with an increased incidence of neonatal hepatitis, usually progressing to cirrhosis.


See Alpha-1-Antitrypsin-A Comprehensive Testing Algorithm in Special Instructions.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

100-190 mg/dL

Interpretation Provides information to assist in interpretation of the test results

Patients with serum levels <70 mg/dL may have a homozygous deficiency and are at risk for early lung disease. Alpha-1-antitrypsin proteotyping should be done to confirm the presence of homozygous deficiency alleles.


If clinically indicated, patients with serum levels <125 mg/dL should be proteotyped in order to identify heterozygous individuals. Heterozygotes do not appear to be at increased risk for early emphysema.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Low alpha-1-antitrypsin (A1A) levels may result from liver disease, and A1A proteotyping should be done to confirm A1A deficiency disease.


A1A is an acute-phase reactant and any inflammatory process will elevate serum A1A levels.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Kanakoudi F, Drossou V, Tzimouli V, et al: Serum concentrations of 10 acute-phase proteins in healthy term and pre-term infants from birth to age 6 months. Clin Chem 1995;41:605-608

2. Morse JO: Alpha-1-antitrypsin deficiency. N Engl J Med 1978;299:1045-1048, 1099-1105

3. Cox DW: Alpha-1-antitrypsin deficiency. In The Metabolic and Molecular Basis of Inherited Disease. Vol 3. Seventh edition. Edited by CR Scriver, AL Beaudet, WS Sly, D Valle. New York, McGraw-Hill Book Company, 1995, pp 4125-4158

Special Instructions and Forms Library of PDFs including pertinent information and consent forms, specimen collection and preparation information, test algorithms, and other information pertinent to test