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Lab Dept:
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Chemistry
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Test Name:
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ALPHA-1-ANTITRYPSIN PHENOTYPE
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General Information
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Lab Order Codes:
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A1AP
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Synonyms:
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A1A Phenotype, serum; AAT Phenotype, serum; Pi Typing; Protease Inhibitor Allo Typing
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CPT Codes:
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82103 - Alpha-1-antitrypsin; total
82104 - Alpha-1-antitrypsin; phenotype
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Test Includes:
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Alpha-1-Antitrypsin, serum reported in mg/dL and phenotype
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Logistics
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Test Indications:
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Useful for identification of homozygous and heterozygous phenotypes of alpha-1-antitrypsin deficiency.
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Lab Testing Sections:
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Chemistry - Sendouts
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Referred to:
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Mayo Medical Laboratories (Test# 26953)
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6280
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651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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2 - 6 days, performed Monday - Friday
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Special Instructions:
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N/A
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Specimen
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Specimen Type:
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Blood
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Container:
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Red top tube
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Draw Volume:
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3 mL (Minimum: 1.5 mL) blood
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Processed Volume:
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1 mL (Minimum: 0.5 mL) serum
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Collection:
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Routine venipuncture
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Special Processing:
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Lab Staff: Centrifuge specimen, remove serum aliquot into a screw-capped round bottom plastic vial. Store and ship at refrigerated temperatures. Forward promptly.
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Patient Preparation:
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None
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Sample Rejection:
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Specimens other than serum, hemolyzed specimens, mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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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.
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Critical Values:
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N/A
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Limitations:
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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.
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Methodology:
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Isoelectric Focusing and Nephelometry
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References:
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Mayo Medical Laboratories Web Page (October 2010)
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