A Critical Comment on a Recent Publication Using Parenchymal Airspace Profiling/Reply: Parenchymal Airspace Profiling Has Its Merits and Is a Valuable Addition to Existing Methods for Lung Morphometry

[...]many of the "shortcomings" that the authors introduce as a motivation for their study have comprehensively been addressed in the American Thoracic Society/European Respiratory Society (ATS/ERS) statement on quantitative assessment of lung structure, and clear recommendations have been made (2). [...]if formalin fixation and paraffin embedding are used, as in the presented study, unpredictable tissue deformation and, above all, shrinkage will occur and introduce a bias for every kind of image analysis (3). [...]simple determination of the 2D area of a distal airspace is not appropriate to separate alveoli and ducts. [...]for simple reasons based on stochastic geometry, it is impossible to estimate the number of objects in a 3D space (such as the number of alveoli) without bias by analyzing only single 2D thin sections. Quantitative assessment of lung structure is demanding and requires careful planning of experiments, regardless of whether stereology or automated image analyses are performed. Copyright © 2017 by the American Thoracic Society Lars Knudsen, M.D. Matthias Ochs, M.D. Hannover Medical School Hannover, Germany Reply: Parenchymal Airspace Profiling Has Its Merits and Is a Valuable Addition to Existing Methods for Lung Morphometry From the Authors: We thank Drs. Knudsen and Ochs for their interest and insightful comments. The American Thoracic Society/European Respiratory Society statement on quantitative assessment of lung structure was taken into consideration before the conception of the parenchymal airspace profiling (PAP) method and was cited in our article (1). [...]since the introduction of the disector method in 1984 by Sterio (3), there have been...