Diagnosis of α-1-Antitrypsin Deficiency: An Algorithm of Quantification, Genotyping, and Phenotyping

Abstract

Background: Laboratory testing in suspected ␣-1-antitrypsin (A1AT) deficiency involves analysis of A1AT concentrations and identification of specific alleles by genotyping or phenotyping. The purpose of this study was to define and evaluate a strategy that provides reliable laboratory evaluation of A1AT deficiency. Methods: Samples from 512 individuals referred for A1AT phenotype analysis were analyzed by quantification, phenotype, and genotype. A1AT concentrations were measured by nephelometry. Phenotype analysis was performed by isoelectric focusing electrophoresis. The genotype assay detected the S and Z deficiency alleles by a melting curve analysis. Results: Of the 512 samples analyzed, 2% of the phenotype and genotype results were discordant. Among these 10 discordant results, 7 were attributed to phenotyping errors. On the basis of these data we formulated an algorithm, according to which we analyzed samples by genotyping and quantification assays, with a reflex to phenotyping when the genotype and quantification results were not concordant. Retrospective analyses demonstrated that 4% of samples submitted for genotype and quantitative analysis were reflexed to phenotyping. Of the reflexed samples, phenotyping confirmed the genotype result in 85% of cases. In the remaining 15%, phenotyping provided further information, including identifying rare deficiency alleles and suggesting

Polymerization and Oxidation of Alpha-1-Antitrypsin in Pathogenesis of Emphysema

“…Therefore it is important to identify appropriate cutoff that balances costs of testing identification of deficiency alleles in the general population. Diagnostic algorithms for laboratory testing of the A1AT deficiency that were proposed (Snyder et al, 2006;Bornhorst et al, 2007;Miravitlles et al, 2010) should lead to improve diagnostics of A1ATD (Figure 4.). Initial testing involves quantification of A1AT concentrations and genotyping.…”

Alpha-1 Antitrypsin Deficiency – A Genetic Risk Factor for COPD

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Alpha One Antitrypsin Deficiency: A Pulmonary Genetic Disorder

“…A1ATD testing can be done via serum and whole blood draw from the vein, but can also be done via a single finger-stick of blood placed onto a card that is mailed into a central lab for testing. A combination of measuring the serum A1AT concentration and performing a PCR based assay to identify S and Z alleles will accurately identify 96% of individuals as compared to the more difficult gold standard isoelectric focusing (Snyder, 2006).…”