Clinics and Departments

Laboratory Services

Lab Dept:

Chemistry

Test Name:

ALPHA-1-ANTITRYPSIN PHENOTYPE

General Information

Lab Order Codes:

A1AP

Synonyms:

A1A Phenotype, serum; AAT Phenotype, serum; Pi Typing; Protease Inhibitor Allo Typing

CPT Codes:

82103 - Alpha-1-antitrypsin; total
82104 - Alpha-1-antitrypsin; phenotype

Test Includes:

Alpha-1-Antitrypsin, serum reported in mg/dL and phenotype

Logistics

Test Indications:

Useful for identification of homozygous and heterozygous phenotypes of alpha-1-antitrypsin deficiency.

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Mayo Medical Laboratories (MML Test: 26953/A1APP)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

2 - 6 days, performed Monday - Friday

Special Instructions:

N/A

Specimen

Specimen Type:

Blood

Container:

Red top tube

Draw Volume:

3 mL (Minimum: 1.5 mL) blood

Processed Volume:

1 mL (Minimum: 0.5 mL) serum

Collection:

Routine venipuncture

Special Processing:

Lab Staff: Centrifuge specimen, remove serum aliquot into a screw-capped round bottom plastic vial. Store and ship at refrigerated temperatures. Forward promptly.

Patient Preparation:

None

Sample Rejection:

Specimens other than serum; hemolyzed specimens; mislabeled or unlabeled specimens

Interpretive

Reference Range:

Alpha-1-Antitrypsin, Serum: 100 - 190 mg/dL

Alpha-1-Antitrypsin Phenotyping: 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.

Interpretation: There are >40 Alpha-1-antitrypsin (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 Caucasians are homozygous M (MM) genotype.

A1A deficiency is usually associated with the Z phenotype (ZZ genotype), but genotypes such as SS and SZ are also associated with decreased A1A levels.

Critical Values:

N/A

Limitations:

This assay does not determine genotype. Genotyping is less variable and more specific than phenotype testing. For genotype testing, refer to Alpha-1-Antitrypsin Genotype (Deficiency) Profile. This testing includes both A1A quantitation and genotyping; phenotyping is automatically performed when the patient’s A1A value and genotype are not diagnostic.

If two bands are seen, such as an M band and a Z band, it is reported as MZ (the equivalent of the genotype).

If one 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.

Methodology:

Isoelectric Focusing and Nephelometry

References:

Mayo Medical Laboratories Web Page (October 2010)



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