When Aplha-1-antitrypsin phenotyping is requested on neonates and it is not possible to collect a 4 mL specimen, 2 EDTA microtainer tubes are acceptable. This only applies in difficult situations. An SST tube must always be collected to allow measurement of alpha-1-antitrypsin.
GENERAL NOTES
APPLICATION: Definitive test for alpha-1-antitrypsin deficiency.
INTERPRETATION: Alpha-1-antitrypsin deficiency is associated with early onset emphysema, hepatitis and cirrohosis and with panniculitis. If deficiency is documented, phenotyping should be done on proband and family. Levels of alpha-1-antitrypsin are increased in an acute phase response and this may mask a deficiency state. If there is a high clinical suspicion of A1AT deficiency, phenotyping should be performed, regardless of the A1AT level. Genetic variants with at least 100 alleles have been described; genotyping is currently available for 2 phenotypes associated with disease: S and Z. Genotyping distinguishes ZZ from Z null or SS from S null patients without the need for family studies.
