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©2013 UpToDate ® Print Email Characteristics of alpha-1 antitrypsin deficiency phenotypes Phenotype Risk for emphysema True plasma level, micromol/L (SI units) Commercial standard plasma level, mg/dL MM (normal) No increase 20 to 48 80 to 220 MZ Possible mild increase 17 to 33 90 to 210 SS No increase 15 to 33 100 to 200 SZ* Mild increase (20 to 50 percent) 8 to 16 75 to 120 • ZZ High risk (80 to 100 percent) 2.5 to 7 20 to 45 Null High risk (100 percent by age 30) 0 0 Pulmonary and plasma features of the different phenotypes of alpha-1 antitrypsin deficiency. Standard commercial measurements of AAT serum levels are obtained by nephelometry. * Heterozygotes with the SZ phenotype rarely have evidence of clinical pulmonary disease. • Protective threshold of 11 micromol/L is approximately equal to a commercial standard level of 80 mg/dL by immunodiffusion (older assay) or ~57 mg/dL by nephelometry. Adapted from: 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; 168:818.