Findings on Thoracic Computed Tomography Scans and Respiratory Outcomes in Persons with and without Chronic Obstructive Pulmonary Disease: A Population-Based Cohort Study.

Background: Thoracic computed tomography (CT) scans are widely performed in clinical practice, often leading to detection of airway or parenchymal abnormalities in asymptomatic or minimally symptomatic individuals. However, clinical relevance of CT abnormalities is uncertain in the general population.
Methods: We evaluated data from 1361 participants aged ≥40 years from a Canadian prospective cohort comprising 408 healthy never-smokers, 502 healthy ever-smokers, and 451 individuals with spirometric evidence of chronic obstructive pulmonary disease (COPD) who had thoracic CT scans. CT images of subjects were visually scored for respiratory bronchiolitis(RB), emphysema(E), bronchial-wall thickening(BWT), expiratory air-trapping(AT), and bronchiectasis(B). Multivariable logistic regression models were used to assess associations of CT features with respiratory symptoms, dyspnea, health status as determined by COPD assessment test, and risk of clinically significant exacerbations during 12 months follow-up.
Results: About 11% of life-time never-smokers demonstrated emphysema on CT scans. Prevalence increased to 30% among smokers with normal lung function and 36%, 50%, and 57% among individuals with mild, moderate or severe/very severe COPD, respectively. Presence of emphysema on CT was associated with chronic cough (OR,2.11; 95%CI,1.4-3.18); chronic phlegm production (OR,1.87; 95% CI,1.27-2.76); wheeze (OR,1.61; 95% CI,1.05-2.48); dyspnoea (OR,2.90; 95% CI,1.41-5.98); CAT score≥10(OR,2.17; 95%CI,1.42-3.30) and risk of ≥2 exacerbations over 12 months (OR,2.17; 95% CI, 1.42-3.0).
Conclusions: Burden of thoracic CT abnormalities is high among Canadians ≥40 years of age, including never-smokers and smokers with normal lung function. Detection of emphysema on CT scans is associated with pulmonary symptoms and increased risk of exacerbations, independent of smoking or lung function.
Competing Interests: DDM, JCH, JMF, DOD, MK, CJH, RR, RC, SA, PL, and LZ have no conflict to declare. JL reports consultancy for CT scans vendors GE, Samsung, and Philips. DDS reports personal fees from Almirall, AstraZeneca, Amgen, and Novatis, and grants from AstraZeneca, outside the submitted work. FM reports grants and personal fees from GSK, Boehringer Ingelheim, and Novartis, and grants from Nycomed, and AstraZeneca during the conduct of the study. KRC reports grants from Novartis, Almirall, Boehringer Ingelheim, Forest, GSK, AstraZeneca, Amgen, Roche, CSL Behring, Grifols, Genentech, and Kamada, during the conduct of the study; and other from CIHR-GSK Research Chair in Respiratory Health Care Delivery, outside the submitted work. PH has received fees for delivering accredited CME and/or consultancy on advisory board for AstraZeneca, Boehringer Ingelheim, Bayer, CSL Behring, Grifols, GlaxoSmithKline, Merck, Novartis, Roche. Dr.Hernandez's institution has received funding for conducting research from Boehringer Ingelheim, Grifols, and CSL Behring. HOC reports personal fees from GSK, and Samsung, and grants from GSK, and Spiration Inc, outside the submitted work. JB and WCT report grants from the Canadian Institute of Heath Research (CIHR/Rx&D Collaborative Research Program Operating Grants- 93326) with industry partners Astra Zeneca Canada Ltd., Boehringer-Ingelheim Canada Ltd, GlaxoSmithKline Canada Ltd, Merck, Novartis Pharma Canada Inc., Nycomed Canada Inc., and Pfizer Canada Ltd., during the conduct of the study. This does not alter our adherence to PLOS ONE policies on sharing data and materials.