Serum Levels of α₁-Antitrypsin Predict Phenotypic Expression of the α₁-Antitrypsin Gene

Author： Steiner Steven Gupta Sandeep Croffie Joseph Fitzgerald Joseph

ISSN： 0163-2116

Source： Digestive Diseases and Sciences, Vol.48, Iss.9, 2003-09, pp. : 1793-1796

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Abstract

We conducted a retrospective analysis to determine if both α₁-antitrypsin serum level and phenotype need be studied when evaluating children for α₁-AT deficiency. We collected data from patients less than 19 years old who had both serum α₁-AT level and phenotype determined over a 9-year period (January 1992–December 2000). Eighty-eight patients were identified and 15 had the PiZZ phenotype. The serum α₁-AT level was below normal (normal 85–215 mg/dl) in all 15 PiZZ patients. Seventy-two of 73 non-PiZZ patients had normal or above normal serum levels. The sensitivity of the serum α₁-AT level was 100%, and the specificity was 99%. The serum α₁-AT level had a positive predictive value of 94% and a negative predictive value of 100%. We conclude that serum α₁-AT levels are highly predictive of the PiZZ phenotype. Determination of the serum α₁-AT level alone should be the initial test when evaluating for α₁-AT deficiency.