Alpha-1-Antitrypsin Phenotype, Serum

CPT CODE:

USEFUL FOR:

Identification of homozygous and heterozygous phenotypes ofthe alpha-1-antitrypsin deficiency

SPECIMEN REQUIRED:

Draw blood in a plain, red-top tube(s) or an serum gel tube(s). Spindown and send 1 mL of serum refrigerated.

TRANSPORT TEMPERATURE:

Refrig\Frozen OK\Ambient NO

CLINICAL INFORMATION:

Alpha-1-antitrypsin (A1A) is the most abundant serum protease inhibitor and inhibits trypsin and elastin, as well as several other proteases. The release of proteolytic enzymes from plasma onto organ surfaces and into tissue spaces results in tissue damage unless inhibitors are present. Congenital deficiency of A1A is associated with the development of emphysema at an unusually early age and with an increased incidence of neonatal hepatitis, usually progressing to cirrhosis.
See "Alpha-1-Antitrypsin - A Comprehensive Testing Algorithm" in Special Instructions.

CLINICAL INTERPRETATION:

There are >40 A1A phenotypes (most of these are associated with normal quantitative levels of protein). The most common normal phenotype is M (M, M1, or M2), and > 90% of Caucasiansare homozygous M (MM) genotype.
A1A deficiency is usually associated with the Z phenotype (ZZ genotype), but genotypes such as SS and SZ are alsoassociated with decreased A1A levels.

REFERENCE VALUES:

ALPHA-1-ANTITRYPSIN

100-190 mg/dL

ALPHA-1-ANTITRYPSIN PHENOTYPE

Most normal individuals have the M phenotype (M, M1, or M2).

Over 99% of M phenotypes are genotypically MM. In the absence

of family studies, the phenotype (M) and quantitative level

can be used to infer the genotype (MM). The most common

alleles associated with a quantitative deficiency are Z and S.

The reports for the rare alleles will indicate whether or not

they have been associated with reduced quantitative levels.