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Alpha-1 Antitrypsin, Plasma

Published: August 9, 2026Updated: August 16, 2026

Measures alpha-1 antitrypsin (AAT), a liver-made protein that protects lung tissue, to help evaluate possible alpha-1 antitrypsin deficiency.

Quick summary

["This blood test helps evaluate whether you may have low alpha-1 antitrypsin, a condition that can affect the lungs and liver."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
1791-3
Short code
AAA Plas Ql
Synonyms
AAA Plas Ql
Category
liver
Sample
plasma
Container
Lavender-top (EDTA) or Green-top (Heparin)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

What is this test?

This test measures alpha-1 antitrypsin (AAT) in plasma, the liquid portion of blood. AAT is a protein made by the liver that helps protect lung tissue from damage.

Why might I need this test?

AAT testing may be ordered for unexplained chronic cough, shortness of breath, recurring lung infections, or family history of alpha-1 antitrypsin deficiency. It may also be considered when liver disease has no clear cause.

How is the test performed?

A blood sample is drawn and processed to separate the plasma. The laboratory then measures the amount of AAT present in the sample.

How do I prepare for the test?

Special preparation is usually not required for this blood test. Tell your healthcare professional if you currently have an infection, inflammation, or liver disease, because these can affect the AAT result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

A low AAT level may indicate inherited alpha-1 antitrypsin deficiency, which can increase the risk of emphysema, chronic bronchitis, and certain forms of liver disease. An elevated level may occur with inflammation or infection and does not necessarily indicate liver injury. An abnormal result may be followed by AAT phenotype or genetic testing to clarify the diagnosis.

Short name

Alpha-1 antitrypsin (AAT) test

Frequently asked questions

What does alpha-1 antitrypsin do?
AAT is a protective protein made by the liver. It helps limit damage to the lungs, particularly from inflammation and harmful chemicals.
Does an abnormal result mean I have alpha-1 antitrypsin deficiency?
Not always. A low result can suggest deficiency, but inflammation and other factors may affect the result, so confirmatory testing may be needed.
Can I prepare for this test by avoiding exercise or alcohol?
Usually no special preparation is needed. Follow any instructions from your healthcare professional, and mention any recent infection, liver disease, or significant inflammation.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy