Molecular diagnostics of α₁-antitrypsin deficiency

Abstract

Diagnosis of α1-antitrypsin (AAT) deficiency is based on serum protein level, phenotyping and genotyping. Each of these methods has serious limitations and not enough accuracy to be used alone. Combinations of two different techniques are recommended to increase the reliability of AAT deficiency testing. Changes of AAT serum levels can result from clinical conditions and the inflammatory response may increase protein level. Phenotyping discriminates AAT variants due to the altered isoelectric point of the protein. It can detect numerous mutations, but often fails in the presence of rare, unknown or null alleles. Genotyping assays can detect or exclude specific mutations. The results are reliable and definitive, but restricted to the most common variants. DNA techniques for AAT gene screening and detection of new variants are available, but these are of limited value as sequencing is required to confirm the results. This review describes common approaches used in AAT deficiency testing and discusses their strengths and weaknesses. A novel functional test for the rapid discrimination of patients with AAT deficiency would greatly enhance diagnostic algorithms.

Immobilized pH gradients

“…In the meantime, most of the clinical biochemistry and forensic medicine typing has switched from phenotype to genotype, taking advantage of the acknowledged features of DNA – stoichiometric presence in all cell types from embryo to adult stage, chemical stability, easy amplification. For instance, for the diagnosis of α 1 ‐antitrypsin deficiency associated with the Z variant (Glu342Lys) different genetic tests – including direct sequencing of PCR amplification products 78, amplification‐reverse hybridization 79 and real‐time PCR 80 – have been proposed.…”