How do you test for alpha-1?

Screening test:

Point of care test: there is an innovative point of care test to screen COPD patients for alpha-1-antitrypsin (A1AT) deficiency (also known as alpha-1) that allows the identification of the Z-AAT protein in the blood, doing it in a fast, quick, and accurate way. If the test result is positive, diagnostic testing is recommended for clarification.

Alpha-1 cannot be diagnosed by symptoms or by medical examination alone.1

Diagnostic testing includes:

  • Quantitative tests for serum A1AT levels2
  • Qualitative tests for the identification of A1AT genetic variants2

Quantitative tests

  • Serum A1AT levels2-4
    • Determined by rocket immunoelectropheresis, radial immunodiffusion, or nephelometry
    • Because A1AT is an acute phase reactant, levels can be misleading
 

Qualitative tests

A genotype/phenotype is recommended along with a serum level test

  • Genotyping by PCR 2,3
    • Identifies the most common abnormal alleles (Z or S)
  • Genotyping by direct sequencing 2,3
    • Identifies null or rare alleles
  • Phenotyping 3
    • Identifies A1AT variants through isoelectric focusing

A decrease in A1AT serum levels increases the risk of emphysema2, 5-7*




 

Although the maintenance of blood serum levels of alpha-1 proteinase inhibitor (PI) (antigenically measured) above 11 μM (or 80 mg/dL [RID]) has been historically postulated to provide therapeutically relevant antineutrophil elastase protection, this has not been proven.

 


Testing methods for alpha-1 are simple, quick and accurate. They enable diagnosis of alpha-1 from a few drops of blood

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References

  1. Alpha-1 Foundation. What is Alpha-1? http://alpha-1foundation.org/what-is-alpha-1/ Accessed July 14, 2014.
  2. Rachelefsky G, Hogarth DK. Issues in the diagnosis of αlpha-1 antitrypsin deficiency. J Allergy Clin Immunol. 2008;121(4):833-838.
  3. American Thoracic Society/European Respiratory Society. American Thoracic Society/European Respiratory Society statement: standards for the diagnosis and management of individuals with alpha-1 antitrypsin deficiency. Am J Respir Crit Care Med. 2003;168(7):818-900.
  4. World Health Organization. alpha-1 antitrypsin deficiency: memorandum from a WHO meeting. Bull World Health Organ. 1997;75(5):397-415.
  5. Brantly ML, Wittes JT, Vogelmeier CF, Hubbard RC, Fells GA, Crystal RG. Use of a highly purified alpha 1-antitrypsin standard to establish ranges for the common normal and deficient alpha-1 antitrypsin phenotypes. Chest. 1991;100:703-708.
  6. Gorrini M, Ferrarotti I, Lupi A, et al. Validation of rapid and simple method to measure α1-antitrypsin in human dried blood spots. Clin Chem. 2006;52:899-901.
  7. Ferrarotti I, Thun GA, Zorzetto M, et al. Serum levels and genotype distribution of α1-antitrypsin in the general population. Thorax. 2012;67:669-674.

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