Genomic DNA extraction from small amounts of serum to be used for α1-antitrypsin genotype analysis

If laboratory diagnosis of alpha(1)-antitrypsin(alpha(1)-AT) deficiency is usually based on its phenotype identification by isoelectric focusing, alpha(1)-antiprotease inhibitor (Pi)S and PiZ genotypes can also be determined by deoxyribonucleic acid (DNA)-based methods. Recently, several methods have been described for preparing genomic DNA from serum. The aim of the current study was to determine the Pi allele from serum extracted DNA by polymerase chain reaction (PCR) and to compare these results with those obtained with whole blood extracted DNA. Serum alpha(1)-AT concentration and phenotypic identification were systematically performed in 43 hospitalised patients. Genomic DNA was simultaneously purified from whole blood and from serum. The mutation detection was found using a PCR-mediated site-directed mutagenesis method. Concerning phenotypic identification, 29 patients were MM homozygotes, 11 were heterozygotes for S (MS=7) or for Z (MZ=4) and three showed a ZZ phenotype. Genotyping analyses gave identical results with serum and whole blood extracted DNA and all the results were in agreement with the phenotyping results. The authors found that the deoxyribonucleic acid-based test proved to be a reliable tool for alpha(1)-antitrypsin deficiency diagnosis and appears to be an alternative for the labour intensive alpha(1)-antitrypsin determination by isoelectric focusing. The authors also concluded that this method yields good quality deoxyribonucleic acid from serum, equal to that extracted from whole blood and is helpful in retrospective studies of multiple genetic markers.