The serum level of alpha-1 antitrypsin correlates with the alleles inherited by the patient.


molecular weight for alpha-1 antitrypsin: 54,000 daltons (some references give 52,000)


1 mg/dL = 0.185 µmole per liter


Note: Standards used in some commercial assays may not be highly purified. Therefore different assays may give different results for the same sample.


Normal Phenotype: MM

Percent of Normal Serum Levels




50 to 100%

MZ, SS, MS, M-null

25 to 49%


5 to 25%

ZZ or Z-null





• The abbreviation PI = proteinase inhibitor.


The risk of emphysema increases significantly when the serum level is < 11 µM (< 60 mg/dL; ATS Table 3 page 825).


Conditions associated with an elevation in serum levels:

(1) acute phase reaction


Conditions associated with a decrease in serum levels:

(1) neonatal respiratory distress syndrome

(2) pancreatitis

(3) liver disease

(4) nephrotic syndrome


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