Each protein in the body starts out as a code in the structure of DNA (a gene). This code is translated into a protein by the protein-synthesizing apparatus of the cell. Individuals with Alpha-1 have at least one abnormal gene and make an abnormal alpha-1 antitrypsin protein… Phenotyping looks at the type of alpha-1 antitrypsin protein floating in the blood and evaluates whether it is normal or abnormal.Big Fat Reference Guide – AlphaNet
So in other words, no, your phenotype is set by your genes and your genes don’t change.
It is interesting to note that individuals on augmentation therapy who have their phenotype re-tested will return a result of PiMZ if they were PiZZ prior to therapy. This is because phenotyping looks at the types of AATprotein in the blood and augmentation therapy delivers normal, PiMM protein to individuals who are PiZZ. Thus phenotype testing will reveal both the Alpha’s own alpha-1 antitrypsin phenotype, as well as the augmentation-delivered normal phenotype. Genotyping, rather than Phenotyping, would be required to determine an individual’s underlying alpha-1 antitrypsin genetics while on augmentation therapy.Big Fat Reference Guide – AlphaNet