Molecular diagnosis of Alpha-1 antitrypsin deficiency: a new method based on Luminex Technology

Background: Alpha-1 antitrypsin deficiency (AATD) is an under-diagnosed hereditary disorder characterized by reduced serum levels of alpha-1 antitrypsin (AAT) and increased risk to develop lung and liver diseases at an early age. AAT is encoded by the highly polymorphic SERPINA1 gene. The most common deficiency alleles are named S and Z, but more than 100 rare variants lead to low levels of the protein. To identify pathological allelic variants, different from S and Z, the sequencing of the gene coding regions is required. Objectives Since sequencing is expensive and time-consuming, we decided to evaluate the accuracy of A1AT Genotyping Test (Progenika, Grifols), a new diagnostic genotyping kit which allows to identify 14 deficiency variants of the SERPINA1 gene (including S and Z) based on Luminex technology. Methods: A total of 418 consecutive samples, with AATD suspicion, were analyzed both by applying the diagnostic algorithm currently in use, and by applying the Progenika assay based on Luminex 200. Results: The Progenika assay gave these results: 101 samples (24,2%) were positive for at least one of the 14 deficiency variants, 316 (75,6%) were negative for all the variants analysed. The identified mutations showed a 100% correlation with the results obtained with our diagnostic algorithm. Seventeen samples (4%) resulted negative for the assay but sequencing identified other rare pathological variants. Conclusions The A1AT Genotyping Test assay resulted to be highly reliable and robust; it allows shorter diagnostic times of response. In certain cases it has been necessary to sequence the SERPINA1 gene to identify other rare mutations not included in the kit.