Finding the right tests…
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Finding the right tests…
Biochemistry
Alpha-1 antitrypsin, or AAT, is a protein made by the liver whose job is to protect lung tissue from an enzyme the immune system releases while fighting inhaled irritants and infection. A genetic condition called AAT deficiency means the liver either makes too little of it or makes a faulty version that gets stuck inside liver cells instead of reaching the bloodstream, and this blood test measures how much properly circulating AAT you actually have. It matters most in two situations doctors wouldn't otherwise connect: unusually early lung disease, especially in a non-smoker, and unexplained liver disease, since the same faulty protein that fails to protect the lungs can build up and damage the liver directly.
The test reports the amount of AAT circulating in your blood, usually alongside genetic testing, from the same or a separate sample, that identifies which version of the SERPINA1 gene you carry. A low blood level on its own suggests deficiency; the genetic result confirms which specific variant is responsible and how significant a risk it carries. Testing can also be done from a finger-prick blood sample or a cheek swab, depending on what the ordering doctor requests.
AAT deficiency follows an inheritance pattern where both copies of the SERPINA1 gene you carry contribute to how much functioning protein reaches your blood. The most common normal version is called M; two less common versions, S and Z, produce reduced amounts of AAT, and someone carrying two copies of the Z version faces the highest risk of both lung and liver disease among the commonly tested variants.
Without enough AAT reaching the lungs, an enzyme called neutrophil elastase, normally kept in check by AAT, is freer to damage lung tissue over time, raising the risk of early emphysema, especially in smokers, but also in people who have never smoked. Separately, the faulty Z-type protein can get physically stuck inside liver cells instead of being released into the blood, which in some people leads to a distinct, unrelated problem: liver scarring, seen in roughly 15 percent of affected adults with this variant, occasionally progressing to cirrhosis.
Because lung symptoms from AAT deficiency can look identical to ordinary asthma or COPD, many affected people are diagnosed with one of those instead and never tested for the underlying cause, especially if they don't fit the typical profile of a long-time smoker in their sixties or seventies. A family history of AAT deficiency, or of early, unexplained lung or liver disease, is a clearer reason to ask for this test specifically rather than assume a more common cause.
People diagnosed with COPD or emphysema at an unusually young age or without a smoking history, people with unexplained chronic liver disease, and close relatives of someone already diagnosed with the condition.
Yes. The faulty Z-type protein can accumulate inside liver cells and cause liver scarring in some affected people, separately from the lung damage that comes from not enough AAT reaching the lungs.
Both are typically used together — a blood level shows whether AAT is low, and genetic testing identifies which SERPINA1 variant you carry and how significant the risk is.
This page is general information about the test, not medical advice. Your own report's reference ranges apply — please discuss your results with your doctor.
Risk depends on which specific combination of gene versions you carry; two copies of the higher-risk Z variant carry the greatest documented risk, and your doctor can explain what your specific result means.
Its lung symptoms can look identical to more common causes of COPD, and the condition itself is uncommon, so it's frequently missed unless a doctor specifically considers it, especially in younger or non-smoking patients.
Yes. Smoking adds further lung irritation on top of the already-reduced protection AAT deficiency provides, which is linked to faster progression of lung damage in affected people.