How to Read Your Alpha-1 Lab Results

When you receive your Alpha-1 lab results, the combination of medical terms can be overwhelming. To understand your complete diagnosis, you need to look at three different measurements that work together: your serum level (how much protein is in your blood), your genotype (your genetic blueprint), and your phenotype (the physical protein your body is making). By combining these three pieces of information, your doctor can determine if you have Alpha-1 antitrypsin deficiency (AATD), how severe it might be, and what risks you face ^[1][2][3].

1. Serum Level: The Amount of Protein

Your serum Alpha-1 antitrypsin level simply measures the total quantity of the Alpha-1 protein currently circulating in your blood ^[4][5]. This is usually the first screening test doctors order ^[1]. Your lab report will provide a “normal” reference range (often around 100–220 mg/dL or 20–53 micromoles, depending on the lab’s measurement system) so you can see if your number falls below the protective threshold ^[4].

However, there is a catch. Alpha-1 antitrypsin is known as an acute-phase reactant, meaning your body naturally produces more of it when you are sick, injured, or experiencing inflammation ^[4][6]. Because of this, if you happen to be fighting off an infection when your blood is drawn, your serum level might look completely normal even if you actually have a genetic deficiency ^[5][6]. Therefore, a serum level alone is not enough to make a definitive diagnosis ^[1].

2. Genotype: Your Genetic Blueprint

Your genotype is your specific DNA makeup, which you inherited from your parents. A genotype test looks directly at the SERPINA1 gene to see exactly which genetic variations (called alleles) you have ^[7][8]. Because it looks at your DNA, this test is highly accurate and is not affected by whether you are sick or healthy ^[7].

Everyone inherits two of these alleles—one from each parent. The most common alleles are assigned letters:

• M allele: This is the “normal” variation. It tells the body to produce normal amounts of healthy Alpha-1 protein ^[9][10].
• S allele: This is a mildly deficient variation ^[9].
• Z allele: This is a severely deficient variation that causes the protein to misfold and get trapped inside your liver, leading to very low levels of the protein in your blood ^[11][10][2].

There are also rare alleles, such as Null alleles, which produce no Alpha-1 protein at all ^[7][8]. If your report lists a letter other than M, S, or Z (such as F, I, or Null), your doctor can help explain how that specific rare variant affects you ^[3].

3. Phenotype: The Physical Protein

While your genotype looks at your DNA blueprint, your phenotype looks at the physical protein that your body is actually producing ^[2][12]. Lab technicians test this by seeing how the proteins move through a gel (a process called isoelectric focusing) ^[2][13]. While direct DNA testing (genotyping) is becoming the standard, phenotype testing remains an important tool to confirm that the proteins in your blood match what your genes suggest, especially if your serum level and genotype do not seem to align ^[3][13][7].

Putting It All Together: Your Lab Results

Your lab report will usually list your results as “Pi” followed by two letters representing the alleles you inherited. “Pi” stands for Protease Inhibitor, which simply refers to a protein that protects your body’s tissues (like your lungs) from damage ^[1][2]. Here is what the most common combinations mean:

• PiMM (Normal): You inherited two normal M genes. Your serum levels should be normal, and you do not have Alpha-1 antitrypsin deficiency ^[1][10].
• PiMS (Carrier / Mild): You inherited one normal M gene and one mildly deficient S gene. While your protein levels might be slightly lower than a PiMM individual, they are generally high enough to protect your lungs and liver, meaning this combination typically does not increase your disease risk ^[1][14].
• PiMZ (Carrier / Intermediate): You inherited one normal M gene and one severely deficient Z gene. Your serum levels will likely be lower than normal ^[1]. While you are a carrier, having PiMZ does increase your risk of developing lung disease (like COPD), especially if you smoke or are exposed to environmental pollutants ^[15][16].
• PiSZ (Intermediate/Severe): You inherited one S gene and one Z gene. This typically results in lower serum levels and a higher risk of disease than PiMZ, but is generally less severe than PiZZ ^[1][17].
• PiZZ (Severe Deficiency): You inherited two Z genes. This results in very low serum levels of Alpha-1 protein in the blood and significantly increases your risk of developing early-onset emphysema and liver disease ^[11][18][19]. If you have this result, doctors will likely discuss lifestyle precautions to protect your lungs and liver, such as avoiding alcohol and never smoking ^[10][15].

Understanding these three components—how much protein you have (serum level), what your DNA says (genotype), and what protein is physically present (phenotype)—allows your healthcare team to accurately diagnose your condition and tailor a monitoring or treatment plan specifically for you ^[1][3].