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

Abstract

BackgroundThoracic 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.MethodsWe 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.ResultsAbout 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).ConclusionsBurden 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.

Bronchiectasis in COPD patients: more than a comorbidity?

“…Moreover, most of these studies excluded patients with previously known bronchiectasis and those with bronchiectasis in only one pulmonary segment, as this circumstance can be found in a significant percentage of elderly people in the general population, or in smokers with no airway obstruction 29. Recently, Tan et al30 found that 19.9% of healthy individuals had bronchiectasis compared with 35.1% of severe COPD patients of the same age. This means that the real prevalence of bronchiectasis in COPD patients might be overestimated, and other CT characteristics such as bronchial wall thickening should be used to differentiate real bronchiectasis in COPD from bronchiectasis associated with aging 14…”

The Impact of Emphysema on Chronic Obstructive Pulmonary Diseases

“…Furthermore, this association remained after compared with the thickness of the airway and showed an even stronger association in the large prospective Canadian Cohort of Obstructive Lung Disease (CanCOLD) where unlike previous studies the data were based on unselected individuals from a random sample from the general population 11 .…”

New therapies for the prevention and treatment of exacerbations of bronchiectasis

“…In independent investigations Tan et al, has shown that bronchiectasis was present in 19.9% of normal never smoking controls without respiratory symptoms, 19.9% of smokers, 14.1% of patients with mild COPD, 22% of patients with moderate COPD and 35.1% of patients with severe or very severe COPD. (14) This indicates that our definition of bronchiectasis may be too sensitive as mild increase in the B-A ratio is observed in 20% of healthy controls, and therefore the true rate of pathological dilatation may be exaggerated. (14) Dias et al recently demonstrated that in the majority of cases of increased B-A ratio in COPD patients, the change in the ratio was due to a reduced size of the blood vessel.…”

“…(14) This indicates that our definition of bronchiectasis may be too sensitive as mild increase in the B-A ratio is observed in 20% of healthy controls, and therefore the true rate of pathological dilatation may be exaggerated. (14) Dias et al recently demonstrated that in the majority of cases of increased B-A ratio in COPD patients, the change in the ratio was due to a reduced size of the blood vessel. These patients therefore do not strictly have bronchiectasis, since the name requires dilation of the bronchi.…”

“…(12)(13)(14) A ratio >1 is usually taken to indicate bronchiectasis. In independent investigations Tan et al, has shown that bronchiectasis was present in 19.9% of normal never smoking controls without respiratory symptoms, 19.9% of smokers, 14.1% of patients with mild COPD, 22% of patients with moderate COPD and 35.1% of patients with severe or very severe COPD.…”