Total Airway Count on Computed Tomography and the Risk of Chronic Obstructive Pulmonary Disease Progression. Findings from a Population-based Study
Authors: Miranda Kirby, Naoya Tanabe, Wan C. Tan, Guohai Zhou, Ma’en Obeidat, Cameron J. Hague, Jonathon Leipsic, Jean Bourbeau, Don D. Sin, James C. Hogg, Harvey O. Coxson, Jean Bourbeau, Wan C. Tan, J. Mark FitzGerald, Don D. Sin, D. D. Marciniuk, D. E. O’Donnell, Paul Hernandez, Kenneth R. Chapman, Robert Cowie, Shawn Aaron, F. Maltais, Jonathon Samet, Milo Puhan, Qutayba Hamid, James C. Hogg, Jean Bourbeau, Carole Baglole, Carole Jabet, Palmina Mancino, Yvan Fortier, Wan C. Tan, Don Sin, Sheena Tam, Jeremy Road, Joe Comeau, Adrian Png, Harvey Coxson, Miranda Kirby, Jonathon Leipsic, Cameron Hague, Mohsen Sadatsafavi, Teresa To, Andrea Gershon, Wan C. Tan, Harvey Coxson, Jean Bourbeau, Pei-Zhi Li, Jean-Francois Duquette, Yvan Fortier, Andrea Benedetti, Denis Jensen, Denis O’Donnell, Wan C. Tan, Christine Lo, Sarah Cheng, Cindy Fung, Nancy Ferguson, Nancy Haynes, Junior Chuang, Licong Li, Selva Bayat, Amanda Wong, Zoe Alavi, Catherine Peng, Bin Zhao, Nathalie Scott-Hsiung, Tasha Nadirshaw, Jean Bourbeau, Palmina Mancino, David Latreille, Jacinthe Baril, Laura Labonte, Kenneth Chapman, Patricia McClean, Nadeen Audisho, Robert Cowie, Ann Cowie, Curtis Dumonceaux, Lisette Machado, Paul Hernandez, Scott Fulton, Kristen Osterling, Shawn Aaron, Kathy Vandemheen, Gay Pratt, Amanda Bergeron, Denis O’Donnell, Matthew McNeil, Kate Whelan, Francois Maltais, Cynthia Brouillard, Darcy Marciniuk, Ron Clemens, Janet Baran
Journal: American Journal of Respiratory and Critical Care Medicine (2017)

Rationale: Studies of excised lungs show that significant airway attrition in the “quiet” zone occurs early in chronic obstructive pulmonary disease (COPD).Objectives: To determine if the total number of airways quantified in vivo using computed tomography (CT) reflects early airway-related disease changes and is associated with lung function decline independent of emphysema in COPD.Methods: Participants in the multicenter, population-based, longitudinal CanCOLD (Canadian Chronic Obstructive Lung Disease) study underwent inspiratory/expiratory CT at visit 1; spirometry was performed at four visits over 6 years. Emphysema was quantified as the CT inspiratory low-attenuation areas below −950 Hounsfield units. CT total airway count (TAC) was measured as well as airway inner diameter and wall area using anatomically equivalent airways.Measurements and Main Results: Participants included never-smokers (n = 286), smokers with normal spirometry at risk for COPD (n = 298), Global Initiative for Chronic Obstructive Lung Disease (GOLD) I COPD (n = 361), and GOLD II COPD (n = 239). TAC was significantly reduced by 19% in both GOLD I and GOLD II compared with never-smokers (P < 0.0001) and by 17% in both GOLD I and GOLD II compared with at-risk participants (P < 0.0001) after adjusting for low-attenuation areas below −950 Hounsfield units. Further analysis revealed parent airways with missing daughter branches had reduced inner diameters (P < 0.0001) and thinner walls (P < 0.0001) compared with those without missing daughter branches. Among all CT measures, TAC had the greatest influence on FEV1 (P < 0.0001), FEV1/FVC (P < 0.0001), and bronchodilator responsiveness (P < 0.0001). TAC was independently associated with lung function decline (FEV1, P = 0.02; FEV1/FVC, P = 0.01).Conclusions: TAC may reflect the airway-related disease changes that accumulate in the “quiet” zone in early/mild COPD, indicating that TAC acquired with commercially available software across various CT platforms may be a biomarker to predict accelerated COPD progression.