Alpha-1 Antitrypsin Phenotype

Diagnostic Use

Identification of homozygous and heterozygous phenotypes of the alpha-1 antitrypsin deficiency.

Alpha-1 antitrypsin phenotyping will be reflex added to all alpha-1 antitrypsin requests for levels if the level is ≤ 1.2 g/L.

Alpha-1 antitrypsin (AAT) 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 AAT is associated with the development of emphysema at an unusually early age and with an increased incidence of neonatal hepatitis, usually progressing to cirrhosis.

Most normal individuals have the M phenotype (M, M1, or M2). Over 99% of M phenotypes are genetically 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.

Department

Protein Lab

Delphic Registration Code

AATP

Constituent Tests

• Alpha-1 Antitrypsin

Turnaround Time

14 days

Test Code

03836

Specimen Type

• Serum
• Plasma

Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Acceptable

• SST II (Gold Cap)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin - Gel (Green Cap)
• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

0.5

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Serum (Red Cap)

Acceptable

• SST II (Gold Cap)
• Lithium Heparin - Non-gel (Green Cap)
• Lithium Heparin - Gel (Green Cap)
• EDTA (Lavender Cap)

Preferred Sample Volume (ml)

0.25

Minimum Sample Volume (ml)

0.25

Aliquot Instructions

Sample Type

• Serum
• Plasma

Minimum Volume (ml)

0.25

Transport to Lab

Chilled (2 - 8 degrees Celsius)

Interpretation

There are greater than 40 alpha-1 antitrypsin (AAT) phenotypes (most of these are associated with normal quantitative levels of protein). The most common normal phenotype is M (M, M1, or M2), and greater than 90% of Caucasians are genetically homozygous M (MM).

AAT deficiency is usually associated with the Z phenotype (homozygous ZZ), but SS and SZ are also associated with decreased AAT concentrations.

This assay identifies the phenotype of the circulating alpha-1 antitrypsin (AAT) protein. If the patient is already on replacement therapy, the phenotype will detect patient and replacement protein.

If 2 bands are seen, such as an M band and a Z bands, it is reported as MZ (eg, heterozygous).

If 1 band is seen, such as the Z band and the quantitative level is consistent with a homozygote, the phenotype is assumed to be homozygous and is reported as ZZ.

Test Method

Isoelectric focusing

Non-Funded Test Cost

$57.50 (Exclusive of GST)

Billing Code

03836

Alpha-1 antitrypsin phenotyping will be reflex added to all alpha-1 antitrypsin requests for levels if the level is ≤ 1.2 g/L.

Repeat phenotyping will not be performed on patients previously phenotyped by CHL, unless there is clinical indication or phenotype results are not concordant with clinical findings.

Contact Information

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