Clinical evaluation of pulmonary quantitative computed tomography parameters for diagnosing eosinophilic chronic obstructive pulmonary disease: Characteristics and diagnostic performance

Abstract Aims To investigate the characteristics and diagnostic performance of quantitative computed tomography (QCT) parameters in eosinophilic chronic obstructive pulmonary disease (COPD) patients. Methods High‐resolution CT scans of COPD patients were retrospectively analyzed, and various emphysematous parenchyma measurements, including lung volume (LC), lung mean density (LMD), lung standard deviation (LSD), full‐width half maximum (FWHM), and lung relative voxel number (LRVN) were performed. The QCT parameters were compared between eosinophilic and noneosinophilic COPD patients, using a definition of eosinophilic COPD as blood eosinophil values ≥ 300 cells·µL −1 on at least three times. Receiver operating characteristic curves and area under the curve (ROC‐AUC) and python were used to evaluate discriminative efficacy of QCT. Results Noneosinophilic COPD patients had a significantly lower TLMD (−846.3 ± 47.9 Hounsfield Unit HU) and TFWHM(162.5 ± 30.6 HU) compared to eosinophilic COPD patients (−817.8 ± 54.4, 177.3 ± 33.1 HU, respectively) ( p = 0.018, 0.03, respectively). Moreover, the total LC (TLC) and TLSD were significantly lower in eosinophilic COPD group (3234.4 ± 1145.8, 183.8 ± 33.9 HU, respectively) than the noneosinophilic COPD group (5600.2 ± 1248.4, 203.5 ± 20.4 HU, respectively) ( p = 0.009, 0.002, respectively). The ROC‐AUC values for TLC, TLMD, TLSD, and TFWHM were 0.91 (95% confidence interval CI, 0.828–0.936), 0.66 (95% CI, 0.546–0.761), 0.64 (95% CI, 0.524–0.742), and 0.63 (95% CI, 0.511–0.731), respectively. When the TLC value was 4110 mL, the sensitivity was 90.7% (95% CI, 79.7–96.9), specificity was 77.8% (95% CI, 57.7–91.4) and accuracy was 86.4%. Notably, TLC demonstrated the highest discriminative efficiency with an F1 Score of 0.79, diagnostic Odds Ratio of 34.3 and Matthews Correlation Coefficient of 0.69, surpassing TLMD (0.55, 3.66, 0.25), TLSD (0.56, 3.95, 0.26), and TFWHM (0.56, 4.16, 0.33). Conclusion Eosinophilic COPD patients exhibit lower levels of emphysema and a more uniform density distribution throughout the lungs compared to noneosinophilic COPD patients. Furthermore, TLC demonstrated the highest diagnostic efficiency and may serve as a valuable diagnostic marker for distinguishing between the two groups.