© 2006 American Thoracic Society
Computed Tomography: A New Gold Standard for the Clinical Assessment of EmphysemaFrom the Authors:
We appreciate the comments of Dr. Parr and colleagues on our recent article (1). We agree that important differences in the study populations are likely responsible for the contrasting conclusions from our study (1) and that of Dawkins and coworkers (2). The National Emphysema Treatment Trial (NETT) included subjects with a severe emphysema phenotype, and thus total emphysema volume was likely centered on a relatively narrow range of severity. This may have limited the ability of emphysema severity to serve as an important discriminator for mortality. On the other hand, the study of Dawkins and coworkers was likely biased toward a population with more uniform expression of lower lobe–dominant disease in contrast to the NETT population, which showed significant variation in upper versus lower distribution and thus may be better designed to determine the impact of distribution independently of emphysema severity. The authors acknowledge, in fact, that the upper lobe distribution in
University of Michigan Medical Center Ann Arbor, Michigan
University of Pittsburgh Pittsburgh, Pennsylvania FOOTNOTES Conflict of Interest Statement: Neither author has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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1-antitrypsin–deficient patients may be a surrogate for disease severity. In our report, we identified disease distribution to be a predictor of survival independently of emphysema severity. The ideal study necessary to further resolve this issue would include a population with both a wide range of disease severity and distribution. Importantly, the results of each paper highlight the importance of using nonconventional parameters such as quantitative computed tomography determinants of disease distribution to refine disease classification and to optimize determination of prognosis in phenotypic subtypes of disease.