Obstructive Lung Diseases |

Quantitative Isoelectric Focusing of Alpha1-Antitrypsin: Grouping and Prevalence of Unusual Alpha1-Antitrypsin Variants FREE TO VIEW

Edward Campbell, MD; Lauren Scott, BS
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Alpha-1 Center, Salt Lake City, UT

Chest. 2013;144(4_MeetingAbstracts):705A. doi:10.1378/chest.1705114
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SESSION TITLE: COPD Diagnosis & Evaluation Posters

SESSION TYPE: Original Investigation Poster

PRESENTED ON: Wednesday, October 30, 2013 at 01:30 PM - 02:30 PM

PURPOSE: Alpha1-antitrypsin (AAT) deficiency is associated with an increased risk for early-onset pulmonary emphysema and for liver disease. Unequivocal clinical diagnosis and classification of AAT deficiency remains a scientific challenge because of the large number of AAT alleles found in the population. Visual examination of isoelectric focusing (IEF) gels has long been used for identification of the common normal (PiM) and the most common abnormal (PiS and PiZ) alleles in clinical samples. However, visual examination alone does not permit identification of the IEF patterns produced by the large number of uncommon abnormal AAT alleles other than PiS and PiZ. We hypothesized that highly accurate quantitative determination of the isoelectric points of the various uncommon AAT alleles will allow grouping and prevalence determination of these alleles in a large population of samples submitted for diagnostic testing.

METHODS: Among 74,509 dried blood spot samples submitted to Alpha1 Center for diagnostic testing in 2010 through 2012, 161 remained incompletely identified after visual examination of IEF gels and genotyping for the 9 most prevalent single point mutations in AAT. Quantitative IEF with QuantityOne® software was retrospectively performed on images of polyacrylamide IEF gels from these samples, using validated isoelectric points for PiM, PiS, and PiZ bands as internal standards.

RESULTS: This innovative method allowed highly accurate determination of the isoelectric points of the unusual AAT alleles that could not be identified by visual interpretation of IEF gels. Grouping of the quantitative IEF data suggested that at least 51 different allele patterns could be identified.

CONCLUSIONS: We have demonstrated the feasibility of highly accurate quantitative IEF of unusual AAT variants. When validated and anchored by DNA sequencing, this method may facilitate the clinical diagnosis of unusual AAT alleles.

CLINICAL IMPLICATIONS: Quantitative IEF will permit enhanced knowledge of the prevalence of the various uncommon AAT alleles, and may find a place in an advanced laboratory algorithm for unequivocal diagnosis of AAT deficiency.

DISCLOSURE: The following authors have nothing to disclose: Edward Campbell, Lauren Scott

We are reporting results from a novel diagnostic evaluation of alpha-1-antitrypsin.




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