Computed tomography total airway count predicts progression to COPD in at-risk smokers

Miranda Kirby; Benjamin M Smith; Naoya Tanabe; James C Hogg; Harvey O Coxson; Don D Sin; Jean Bourbeau; Wan C Tan

doi:10.1183/23120541.00307-2021

Computed tomography total airway count predicts progression to COPD in at-risk smokers

ERJ Open Res. 2021 Oct 25;7(4):00307-2021. doi: 10.1183/23120541.00307-2021. eCollection 2021 Oct.

Authors

Miranda Kirby^{1

2}, Benjamin M Smith^{3

4

5}, Naoya Tanabe², James C Hogg², Harvey O Coxson², Don D Sin², Jean Bourbeau^{6

7}, Wan C Tan²

Affiliations

¹ Dept of Physics, Ryerson University, Toronto, ON, Canada.
² UBC Centre for Heart Lung Innovation, St Paul's Hospital, Vancouver, BC, Canada.
³ Dept of Medicine, McGill University, Montreal, QC, Canada.
⁴ Dept of Epidemiology, Biostatistics, and Occupational Health, McGill University, Montreal, QC, Canada.
⁵ Dept of Medicine, Columbia University Medical Center, New York, NY, USA.
⁶ Montreal Chest Institute of the Royal Victoria Hospital, McGill University Health Centre, Montreal, QC, Canada.
⁷ Respiratory Epidemiology and Clinical Research Unit, Research Institute of McGill University Health Centre, Montreal, QC, Canada.

Abstract

There is limited understanding of how to identify people at high risk of developing COPD. Our objective was to investigate the association between computed tomography (CT) total airway count (TAC) and incident COPD over 3 years among ever-smokers from the population-based Canadian Cohort Obstructive Lung Disease (CanCOLD) study. CT and spirometry were acquired in ever-smokers at baseline; spirometry was repeated at 3-year follow-up. CT TAC was generated by summing all airway segments in the segmented airway tree (VIDA Diagnostics, Inc.). CT airway wall area, wall thickness for a theoretical airway with 10 mm perimeter (Pi10), and low attenuation areas below -856 HU (LAA₈₅₆) were also measured. Logistic and mixed effects regression models were constructed to determine the association for CT measurements with development of COPD and forced expiratory volume in 1 s/forced vital capacity (FEV₁/FVC) decline, respectively. Among 316 at-risk participants evaluated at baseline (65±9 years, 40% female, 18±19 pack-years), incident COPD was detected in 56 participants (18%) over a median 3.1±0.6 years of follow-up. Among CT measurements, only TAC was associated with incident COPD (p=0.03), where a 1-sd decrement in TAC increased the odds ratio for incident COPD by a factor of two. In a multivariable linear regression model, reduced TAC was significantly associated with greater longitudinal FEV₁/FVC decline (p=0.03), but no other measurements were significant. CT TAC predicts incident COPD in at-risk smokers, indicating that smokers exhibit early structural changes associated with COPD prior to abnormal spirometry.