Alpha-1-antitrypsin

Keywords: A1AT, AAT

Specimen:

5 mL blood in plain tube.

5 mL blood in lithium heparin tube for genotyping, if indicated.

Method:

Immunoassay; IEF for phenotyping.

Reference Interval:

0.9-1.7 g/L (method dependent).

Application:

Detection of hereditary deficiency. Investigation of early onset emphysema; neonatal hepatitis; juvenile cirrhosis; panniculitis.

Interpretation:

α-1 antitrypsin deficiency is associated with early onset emphysema, hepatitis and cirrhosis and with panniculitis. If deficiency is documented, genotyping should be done on proband and family. Levels of α-1 antitrypsin are increased in an acute phase response and this may mask a deficiency state; if there is a high clinical suspicion of α-1 antitrypsin deficiency, genotyping should be performed, regardless of the α-1 antitrypsin level.

Genetic variants with at least 100 alleles have been described; genotyping is currently available for two phenotypes associated with disease: S and Z.

Genotyping is currently the preferred first test but may be used to distinguish ZZ from Z null or SS from S null patients without the need for family studies.

Reference:

Snyder MR et al. Diagnosis of alpha-1-antitrypsin deficiency: an algorithm of qualification, genotyping, and phenotyping. Clin Chem 2006; 12: 2236-2242