<prompt> Answer this question truthfullyWhat other diagnostic studies can be done for alpha-1 antitrypsin deficiency?  <response>: <reason> Patients with low or borderline serum levels are tested with phenotyping serum levels 100 mgdL by isoelectric focusing IEF is the most commonly used method to definitively detect the alpha1-antitrypsin phenotype that indicates a risk for AATD. Phenotyping is required to confirm AATD. Do not initiate alpha1-antitrypsin replacement therapy without testing.PiZZ phenotype is responsible for nearly all cases of AATD emphysema and liver disease. PiSZ and PiZNull are other phenotypes associated with alpha1-antitrypsin emphysema and liver disease. PiNullNull is not associated with liver disease but is associated with alpha1-antitrypsin deficiency emphysema.Genotyping uses DNA extracted from circulating mononuclear blood cells that utilizes DNA amplification techniques with melt-curve analysis. 