Analysis of emphysema severity and emphysema characteristics using quantitative computed tomography in patients with alpha-1 antitrypsin deficiency

<bold>Introduction:</bold> In patients with severe alpha-1-antitrypsin deficiency (AATD) of the Pi*ZZ type, quantitative CT analysis (QCT) is the imaging technique of choice for the objective assessment of emphysema severity. For patients with rare allele variants associated with severe AATM, there is hardly any data available. <bold>Methods:</bold> We included patients with complex heterozygous AATM and the presence of at least one rare allele variant, genotype Pi*ZZ or Pi*SZ. The MDCT files were segmented using the fully automated, knowledge-based software YACTA, whereby the lobe-specific emphysema index (EI% -950 HU) and the arrangement of the emphysema voxels (bullous, paraseptal and panlobular) were examined. <bold>Results:</bold> 46 patients, 45% female, aged 56.9±19.0 years were examined. 29 had Pi*ZZ type (63.0%), 8 had Pi*SZ type and 9 had rare allele variants (Q0HeidelbergI-IV, MProcida, MNichinan, Q0-Clayton, Q0Granite Falls and P-Lowell). The Pi*SZ group tended to show lower indices with 27.1±15.0% and 27.5±19.4% vs. 15.8±17.2% (p=0.063). The lobe-specific EI% showed an emphasis on the right lower lobe (29.3±21.3% vs. 14.1±14.3%; p=0.067) and the middle lobe (36.6±24.1% vs. 15.6±13.2%; p=0.038) in patients with severe AATM compared to Pi*SZ. With regard to emphysema characteristics, they showed more bullous (25.1±17.6% vs. 14.2±10.9%; p=0.063) and significantly more panlobular emphysema (8.7±8.9% vs. 19.4±15.6%; p=0.048). <bold>Conclusion:</bold> Quantitative CT with determination of the lobe-specific EI can help to identify clinically relevant phenotypes in patients with different AATM genotypes.