New Method Of Alpha-1-Antitrypsin Diagnosis Facilitates The Detection Of Rare Mutations

Introduction: Alpha-1-antitrypsin deficiency (AATD) is a rare hereditary disease resulting from mutations in the SERPINA1 (serine protease inhibitor) gene and is characterized by low AAT serum levels. Among the more than 100 known mutations of SERPINA1, the Z- and the S-Allele are the most frequent mutations leading to AATD. Different PCR-based methods can be used in laboratory practice. Aims and Objectives: The study provides a comparison of the results (AATD laboratory of the University of Marburg) after the introduction of a new diagnostic genotyping kit (Progenika A1AT Genotyping Test) as compared to the conventional PCR-based algorithm before the introduction of the test. Methods: In July 2016, a new method has been established (Luminex xMAP-based multiplex PCR), allowing the detection of 14 SERPINA1 mutations, while in the time period before July 2016, genotyping was performed with a PCR-analysis for the presence of the S- and Z-mutation only. Isoelectric focusing (IEF) of serum or “dried-blood-spot” (DBS) and/or sequencing was used to diagnose unclear cases. We compared the AAT-genotypes of all 8,137 patients diagnosed by Luminex-based multiplex PCR to the same number of patients before July 2016. Results: Using multiplex PCR, we found 8,056 genotypes without sequencing, including 392 rare (of the 14 mutations) and 68 other (rare or new). In 8,137 individuals, analyzed before the introduction of the new test, only 7,836 could be diagnosed directly, and 301 had to be sequenced (finding 270 rare and 25 new mutations). Conclusion: The introduction of a new Luminex-based multiplex PCR leads to a marked reduction of samples that need to be sequenced, thus simplifies the diagnostic algorithm.