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HelpTest Code A1APP Alpha-1-Antitrypsin Phenotype, Serum
Reporting Name
Alpha-1-Antitrypsin PhenotypeUseful For
Identification of homozygous and heterozygous phenotypes of the alpha-1-antitrypsin deficiency
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| A1AP2 | Alpha-1-Antitrypsin Phenotype | No | Yes |
| AATP | Alpha-1-Antitrypsin, S | Yes, (Order AAT) | Yes |
Testing Algorithm
See Alpha-1-Antitrypsin-A Comprehensive Testing Algorithm in Special Instructions.
Method Name
A1AP2: Isoelectric Focusing
AATP: Nephelometry
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
SerumSpecimen Required
Collection Container/Tube:
Preferred: Red top
Acceptable: Serum gel
Submission Container/Tube: Plastic vial
Specimen Volume: 1.25 mL
Collection Instructions: Centrifuge and aliquot serum into a plastic vial.
Specimen Minimum Volume
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Serum | Refrigerated (preferred) | 28 days | |
| Ambient | 28 days | ||
| Frozen | 28 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Gross icterus | OK |
Special Instructions
Reference Values
ALPHA-1-ANTITRYPSIN
100-190 mg/dL
ALPHA-1-ANTITRYPSIN PHENOTYPE
The interpretive report will identify the alleles present. For rare alleles, the report will indicate whether or not they have been associated with reduced quantitative levels of alpha-1-antitrypsin.
Day(s) Performed
Monday through Friday
CPT Code Information
82103
82104
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| A1APP | Alpha-1-Antitrypsin Phenotype | 32769-2 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| AATP | Alpha-1-Antitrypsin, S | 6771-0 |
| 8166 | Alpha-1-Antitrypsin Phenotype | 32769-2 |
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.
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.
See Alpha-1-Antitrypsin-A Comprehensive Testing Algorithm in Special Instructions.
Interpretation
There are greater than 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 greater than 90% of individuals of European descent are genetically homozygous M (MM).
A1A deficiency is usually associated with the Z phenotype (homozygous ZZ), but SS and SZ are also associated with decreased A1A levels.
Cautions
This assay identifies the phenotype of the circulating alpha-1-antitrypsin (A1A) 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.
Method Description
Phenotyping is done by isoelectric focusing in agarose gels.(Package insert: Hydragel 18 A1AT Isofocusing. Sebia. 2013 July)
Nephelometry.(Instruction manual: Siemens Nephelometer II. Siemens, Inc., Newark, DE)