α₁-Antitrypsin

Serum (preferred) or plasma

1 mL

0.3 mL (Note: This volume does not allow for repeat testing.)

Red-top tube, gel-barrier tube, lavender-top (EDTA) tube, or green-top (heparin) tube

Overnight fasting is preferred.

Detection of hereditary decreases in the production of α₁-antitrypsin (α₁AT). Decreased or nearly absent levels of α₁AT can be a factor in chronic obstructive lung disease and liver disease. An increased prevalence of non-MM phenotypes is found with cryptogenic cirrhosis and with CAH. Cirrhosis in a child should raise consideration of α₁AT deficiency or Wilson's disease. Diagnosis of inflammatory states, if elevated (eg, rheumatoid arthritis, bacterial infection, vasculitis, neoplasia).

α₁AT may be elevated into normal range in heterozygous deficient patients during concurrent infection, pregnancy, estrogen therapy, steroid therapy, cancer, and during postoperative periods. Homozygous deficient patients will not show such elevation. Normal α₁AT levels may occur in patients with liver disease who are heterozygotes. In normals, pregnancy and contraceptive medication may elevate levels. Levels are normally low at birth but rise soon thereafter.

Immunologic

See table.

Should be run when α₁-globulin in serum protein electrophoresis is low or when two bands are seen in the α₁-region. Heterozygous patients exhibit AAT levels which are commonly about 60% of normal. Homozygous recessive α₁AT patients exhibit levels at about 10% of normal. Phenotyping is desirable on patients with low values and on all patients being worked up for AAT-deficient liver disease. Most pathologic is homozygous state ZZ. An M null genotype will have phenotype as MM but low serum level. AAT is one of the alpha-globulins, which together are called “acute phase reactants.” These rise rapidly, but nonspecifically, in response to inflammatory insults.