Diagnosis of chronic obstructive pulmonary disease in lung cancer screening Computed Tomography scans: independent contribution of emphysema, air trapping and bronchial wall thickening

Abstract

BackgroundBeyond lung cancer, screening CT contains additional information on other smoking related diseases (e.g. chronic obstructive pulmonary disease, COPD). Since pulmonary function testing is not regularly incorporated in lung cancer screening, imaging biomarkers for COPD are likely to provide important surrogate measures for disease evaluation. Therefore, this study aims to determine the independent diagnostic value of CT emphysema, CT air trapping and CT bronchial wall thickness for COPD in low-dose screening CT scans.MethodsPrebronchodilator spirometry and volumetric inspiratory and expiratory chest CT were obtained on the same day in 1140 male lung cancer screening participants. Emphysema, air trapping and bronchial wall thickness were automatically quantified in the CT scans. Logistic regression analysis was performed to derivate a model to diagnose COPD. The model was internally validated using bootstrapping techniques.ResultsEach of the three CT biomarkers independently contributed diagnostic value for COPD, additional to age, body mass index, smoking history and smoking status. The diagnostic model that included all three CT biomarkers had a sensitivity and specificity of 73.2% and 88.%, respectively. The positive and negative predictive value were 80.2% and 84.2%, respectively. Of all participants, 82.8% was assigned the correct status. The C-statistic was 0.87, and the Net Reclassification Index compared to a model without any CT biomarkers was 44.4%. However, the added value of the expiratory CT data was limited, with an increase in Net Reclassification Index of 4.5% compared to a model with only inspiratory CT data.ConclusionQuantitatively assessed CT emphysema, air trapping and bronchial wall thickness each contain independent diagnostic information for COPD, and these imaging biomarkers might prove useful in the absence of lung function testing and may influence lung cancer screening strategy. Inspiratory CT biomarkers alone may be sufficient to identify patients with COPD in lung cancer screening setting.

Airway wall thickness associated with forced expiratory volume in 1 second decline and development of airflow limitation

“…The square root of wall area for a theoretical airway with 10-mm lumen perimeter was calculated, which was used as a measurement of airway wall thickness. Reproduced from [21] with permission from the publisher.…”

“…A linear regression of the square root of wall area versus the lumen perimeter was calculated for all cross-sections ( fig. 1) [21]. The square root of wall area of a 10-mm lumen perimeter (Pi10) was calculated and used as a measurement of airway wall thickness.…”

Computed tomography quantification of tracheal abnormalities in COPD and their influence on airflow limitation

“…Disease severity is evaluated by comparing the postbronchodilator FEV 1 value with its predicted value to assign the patients to one of the stages defined by the Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) ranging from stage 1 (mild COPD) to stage 4 (severe COPD) . However, COPD is a heterogeneous disease and the data obtained from PFT do not allow for differentiation between subtypes such as airway‐dominant or emphysematous phenotypes …”

The path to personalised medicine in COPD

“…Whether or not the routine management of patients with COPD should involve this sort of imaging technique is currently unclear. However, as an example, a single CT scan can provide information on the presence of emphysema,61 lung cancer,62 bronchiectasis63 and coronary artery calcification,64 as well as others such as pulmonary emboli, column osteoporosis and pectoralis muscle mass. All of them are clinically relevant and potentially actionable (ie, treatable).…”