Alpha-1-antitrypsin deficiency

Diagnosis and Testing

What does testing for alpha-1 antitrypsin deficiency involve?

Only blood testing can determine if someone has alpha-1 antitrypsin deficiency (AATD). A medical exam alone cannot determine whether someone has AATD. Additionally, some people who have changes, or mutations, in the gene for AATD (called SERPINA1) stay healthy for some or all of their lives. Genetic testing requires a blood sample, which may be taken by a finger stick or by a standard blood draw. The laboratory will do one or more of the following tests on your blood sample:

  • Immunoassay (AAT Level). This measures the amount of alpha-1 protein in your blood. This indicates if you have a normal, intermediate, or very low amount of alpha-1 circulating in your blood.
  • Phenotyping. This is a protein typing test. This test determines the types of proteins in your blood. This result is in the form of two letters. M (normal) would mean that only M protein was detected. MZ (carrier) would mean both M and Z were detected. Z (abnormal) would mean only Z was detected. Because the proteins produced are determined by genes, protein types correspond with gene types (genotype) in most cases. There are many possible phenotyping results that correspond with the 150+ gene types for alpha-1.
  • Genotyping. This test looks for specific mutations in your SERPINA1 gene. Genotyping always looks for the most common mutation, called "Z." Some genotyping tests look for additional mutations, such as S, F, I and others. Genotype results are usually given as two letters (such as MM, MZ, ZZ). Each letter indicates an inherited code for how your body will produce AAT. Anyone reviewing results should be cautious, as a normal M allele is often reported if other mutations (a limited number) looked for are not seen. Therefore, someone may still have a risk for rare mutations, especially if there are known rare mutations in the family.
  • Gene Sequencing. This test is more detailed than genotyping and can find very rare changes in the SERPINA1 gene. This testing may be offered if an unusual result is found on earlier testing, or if a SERPINA1 gene mutation is already known to be in the family.

The above tests can determine whether you inherited AATD, which is a genetic predisposition to lung and liver disease. Additional medical tests with your doctor are needed to determine whether you actually have lung or liver disease. Most people with AATD do not have symptoms for much of their life, despite being born with the condition.

Alpha-1 at MUSC: A shared voice for patient empowerment. Retrieved from

Alpha-1 Antitrypsin Deficiency. GeneReviews. Retrieved August 28, 2017 from

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