Structural and functional changes in COPD: What we have learned from imaging

Quantitative CT imaging characteristics of patients with chronic obstructive pulmonary disease with different eosinophil levels: a retrospective observational study using linked data from a tertiary hospital in China

OBJECTIVE

To investigate the relationship between eosinophil (EOS) and CT imaging, we quantitatively evaluated the bronchial wall thickening, emphysema index (EI) and pulmonary vascular parameters in patients with chronic obstructive pulmonary disease (COPD) based on different EOS levels.

DESIGN

Retrospective observational study.

SETTING

A tertiary hospital in China.

PARTICIPANTS

448 patients with COPD from January 2020 to January 2023.

MAIN OUTCOME MEASURES

Laboratory data, chest CT and pulmonary function based on different EOS levels: <150/µL, ≥150/µL; <100/µL, 100-300/µL, ≥300/µL; <2%, ≥2%.

RESULTS

We evaluated the records of 448 patients diagnosed with COPD. The prevalence of eosinophilia with EOS ≥2% was 41.1% (184 cases), 33.7% (151 cases) with EOS ≥150/µL and 9.4% (42 cases) with EOS ≥300/µL. A lower EOS (EOS <2% or EOS <150/µL) was associated with chronic pulmonary heart disease. The neutrophil count and percentage were significantly higher in the relatively lower EOS group (EOS <2%, EOS <150/µL or EOS <100/µL). When the groups were divided based on the two cut-off values of 2% of EOS percentage and 150/µL of absolute EOS value, no statistical significance was observed for the entire lung, left lung, right lung, lung lobe volume, lung index (EI), and lung emphysema heterogeneity index (HI). However, compared with the 100-300/µL group, the EI of the right upper lobe of the lung was lower in the EOS ≥300/µL group (0.32 vs 0.37, p<0.05). Airway wall thickness, wall area percentage and Pi10 in the EOS ≥2%, EOS ≥150/µL and 100-300/µL groups were lower than those in the EOS <2%, EOS <150/µL and EOS <100/µL groups, respectively. Compared with the EOS <100/µL group, Pi10 in the EOS ≥300/µL group was lower. According to the different cut-off values, such as percentage and absolute value of EOS, there was no significant difference in pulmonary vascular parameters, such as in cross-sectional area less than 5 mm2 (BV5), total blood volume (TBV), BV5/TBV, network length, branchpoints and endpoints (p>0.05 for both). The per cent predicted diffusing lung capacity for carbon monoxide (DLCO%) of the EOS ≥2% group was higher than that of the EOS <2% group. Compared with patients with blood EOS <150/µL, patients with blood EOS ≥150/µL had lower residual volume and lung volume ratio and higher values for per cent predicted forced vital capacity and DLCO%. The values for per cent predicted forced expiratory volume in 1 s, maximal expiratory flow at 75%/50%/25% of lung volume (MEF75%,MEF50%, MEF25%) and DLCO% in the EOS ≥300/µL group were higher than those in the EOS <100/µL group and in the 100-300/µL group.

CONCLUSIONS

Hypereosinophilic COPD (EOS ≥2% or EOS ≥150/µL or EOS ≥300/µL) appears to have less bronchial thickening and better lung function. Notably, in patients with EOS ≥300/µL, the EI of the right upper lobe is reduced. These findings provide valuable insights into the role of EOS in COPD pathophysiology.

[CT imaging of chronic obstructive pulmonary disease: What aspects and what role?]

Chronic obstructive pulmonary disease (COPD), commonly defined as irreversible airflow limitation, is associated with specific morphological changes involving all three parts of the lung, namely the bronchi, parenchyma and pulmonary vessels. In vivo imaging, with its ability to describe the different types of lung alterations and their regional distribution, helps to elucidate the relationship between lung structure and respiratory function. High-resolution computed tomography (CT) of the lung is the imaging modality best suited to assessing the pathological changes associated with airflow obstruction occurring in COPD. Over the last few decades, numerous studies have demonstrated the role of CT as a morphological and functional method conducive to the phenotyping of COPD patients. This review proposes to examine the data on CT imaging of COPD with a critical approach to recent data, and to determine the extent to which CT could be integrated into care or clinical research on patients with this/these disease(s).

Differential decline of lung function in COPD patients according to structural abnormality in chest CT

BACKGROUND

Different progressions or prognoses of chronic obstructive pulmonary disease (COPD) have been reported according to structural abnormalities based on chest computed tomography (CT). This study aimed to investigate whether different structural abnormalities independently affect annual lung function changes and clinical prognosis in patients with COPD.

METHODS

This longitudinal multicenter observational study was conducted using the KOCOSS cohort (NCT02800499) database in Korea from January 2012 to December 2019. For COPD patients with chest CT findings at baseline enrolment and longitudinal spirometric data, annual forced expiratory volume in 1 s (FEV1) decline rate (mL/year) and clinical outcomes were compared according to structural abnormalities, including emphysema, bronchiectasis (BE), and tuberculosis-destroyed lung (TDL). We estimated the adjusted annual FEV1 changes using a mixed-effect linear regression model.

RESULTS

Among the enrolled 237 patients, 152 showed structural abnormalities. Emphysema, BE, and TDL were observed in 119 (78.3%), 28 (18.4%), and 27 (17.8%) patients, respectively. The annual decline in FEV1 was faster in COPD patients with structural abnormalities than those without (β = -70.6 mL/year, P-value = 0.039). BE/TDL-dominant or emphysema-dominant structural abnormality contributed to an accelerated annual FEV1 decline compared to no structural abnormality (BE/TDL-dominant, β = -103.7 mL/year, P-value = 0.043; emphysema-dominant, β = -84.1 mL/year, P-value = 0.018). Structural abnormalities made no significant differences in acute exacerbation rate and mortality.

CONCLUSION

The lung function decline rate in COPD differed according to structural abnormalities on CT. These findings may suggest that more focus should be placed on earlier intervention or regular follow-up with spirometry in COPD patients with BE or TDL on chest CT.

Genome-Wide Association Study of Airway Wall Thickening in a Korean Chronic Obstructive Pulmonary Disease Cohort

Airway wall thickening (AWT) plays an important pathophysiological role in airway diseases such as chronic obstructive pulmonary disease (COPD). There are only a few studies on the genetic components contributing to AWT in the Korean population. This study aimed to identify AWT-related single-nucleotide polymorphisms (SNPs) using a genome-wide association study (GWAS). We performed GWAS for AWT using the CODA and KUCOPD cohorts. Thereafter, a meta-analysis was performed. Airway wall thickness was measured using automatic segmentation software. The AWT at an internal perimeter of 10 mm (AWT-Pi10) was calculated by the square root of the theoretical airway wall area using the full-width-half-maximum method. We identified a significant SNP (rs11648772, p = 1.41 × 10^-8) located in LINC02127, near SALL1. This gene is involved in the inhibition of epithelial-mesenchymal transition in glial cells, and it affects bronchial wall depression in COPD patients. Additionally, we identified other SNPs (rs11970854, p = 1.92 × 10^-6; rs16920168, p = 5.29 × 10^-6) involved in airway inflammation and proliferation and found that AWT is influenced by these genetic variants. Our study helps identify the genetic cause of COPD in an Asian population and provides a potential basis for treatment.