Featured Biomarker
Alpha-1-antitrypsin
Alpha-1-antitrypsin (AAT) is a protein made in the liver that protects the liver and the lungs so they can work normally. Alpha-1-antitrypsin is a member of the protease inhibitor family. Other protease inhibitors are trypsin, chymotrypsin, and elastase. An inherited deficiency of AAT can potentially be associated with liver disease (cirrhosis) or lung disease (emphysema). Lung symptoms associated with AAT deficiency can mimic asthma in some people. Increased levels may be associated with inflammation. Thus, AAT levels should always be viewed in conjunction with CRP because if a person's CRP is elevated, their AAT may be falsely elevated.
- AAT is a member of the serine protease inhibitor family and its function is to inhibit proteases.
- Although it is named Alpha - 1 Antitrypsin, the most important protease it inhibits is neutrophil elastase (NE).
- AAT is produced in the liver.
- Individuals with the Z genotype variant produce a normal amount of AAT, however only about 15% of the AAT produced by the hepatocytes is released into the circulation. The remaining 85% accumulates in the liver.
- Individuals with significantly reduced serum levels of AAT can develop cirrhosis, C-ANCA vasculitis, and emphysema.
- C-ANCA vasculitis is caused by NE attacking vessel walls, especially within the glomerulus (i.e. C-ANCA glomerulonephritis).
- AAT is an acute phase reactant. Therefore, individuals with mild AAT deficiency may have normal levels of AAT during an episode of acute inflammation.
- It is recommended not to rely on the serum level of AAT if the CRP is elevated.
- Falsely elevated AAT levels can also occur as the result of pregnancy, estrogen therapy (BCP or HRT), or liver disease.
- Prevalence in the United States
* Sources: Alpha-1 Foundation, American Thoracic Society, and Jacobs & DeMott Laboratory Test Handbook