Alpha₁-Antitrypsin and Alpha₁-Antitrypsin Phenotyping

General

Synonym/Acronym:
Alpha1-antitrypsin: A1 AT, alpha1-AT, AAT; alpha1-antitrypsin phenotyping: A1 AT phenotype, alpha1-AT phenotype, AAT phenotype, Pi phenotype.

Rationale
To assist in the identification of chronic obstructive pulmonary disease (COPD) and liver disease associated with alpha1-antitrypsin (alpha1-AT) deficiency.

Patient Preparation
There are no food, fluid, or activity restrictions unless by medical direction. Oral contraceptives should be withheld 24 hr before the specimen is collected, although this restriction should first be confirmed with the health-care provider (HCP) ordering the test.

Normal Findings
Method: Nephelometry for alpha1-AT, isoelectric focusing/high-resolution electrophoresis for alpha1-AT phenotyping.

Alpha1-Antitrypsin

AgeConventional UnitsSI Units (Conventional Units × 0.01)
Newborn145–270 mg/dL1.45–2.7 g/L
Child110–157 mg/dL1.11.579 g/L
Adult100–190 mg/dL11.9 g/L

Alpha1-Antitrypsin Phenotyping
There are three major protease inhibitor phenotypes:

  • MM—Normal
  • SS—Intermediate; heterozygous
  • ZZ—Markedly abnormal; homozygous



The total level of measurable alpha1-AT varies with genotype. The effects of alpha1-AT deficiency depend on the patient’s personal habits but are most severe in patients who smoke tobacco.Critical Findings and Potential Interventions
N/A

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