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 AATalpha-1 antitrypsin protein 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 AATalpha-1 antitrypsin phenotype, as well as the augmentation-delivered normal phenotype. Genotyping, rather than Phenotyping, would be required to determine an individual’s underlying AATalpha-1 antitrypsin genetics while on augmentation therapy.
An interesting note – Big Fat Reference Guide