Isoelectric focusing may be used to genotype the SERPINA1 gene, including the PiMM genotype having normal AAT concentrations, the PiMZ genotype with mild AAT deficiency, and the PiZZ genotype with severe AAT deficiency (Global initiative for Chronic Obstructive Lung Disease, 2020). This evidence concerns the gene SERPINA1 and alpha 1-antitrypsin deficiency.