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Test ID: AAT Alpha-1-Antitrypsin, Serum

Reporting Name

Alpha-1-Antitrypsin, S

Useful For

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


Diagnosis of alpha-1-antitrypsin deficiency

Testing Algorithm

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

Specimen Type


Specimen Required


Preferred: Red top

Acceptable: Serum gel

Specimen Volume: 1 mL

Specimen Minimum Volume

0.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Serum Refrigerated (preferred) 28 days
  Ambient  28 days
  Frozen  28 days

Reference Values

100-190 mg/dL

Day(s) Performed

Monday through Friday

Test Classification

This test has been cleared, approved, or is exempt by the US Food and Drug Administration and is used per manufacturer's instructions. Performance characteristics were verified by Mayo Clinic in a manner consistent with CLIA requirements.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
AAT Alpha-1-Antitrypsin, S 6771-0


Result ID Test Result Name Result LOINC Value
AAT Alpha-1-Antitrypsin, S 6771-0

Clinical Information

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.


Patients with serum levels less than 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 less than 125 mg/dL should be proteotyped in order to identify heterozygous individuals. Heterozygotes do not appear to be at increased risk for early emphysema.

Clinical Reference

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: Scriver CR, Beaudet AL, Sly WS, Valle D, eds. The Metabolic and Molecular Basis of Inherited Disease. Vol 3. 7th ed. McGraw-Hill Book Company; 1995:4125-4158

Report Available

1 to 2 days

Method Name



If not ordering electronically, complete, print, and send a Gastroenterology and Hepatology Client Test Request (T728) with the specimen.

Mayo Clinic Laboratories | Gastroenterology Catalog Additional Information: