Emphysema extent on computed tomography is a highly specific index in diagnosing persistent airflow limitation: a real-world study in China

Abstract

ObjectiveThe diagnostic value of emphysema extent in consistent air flow limitation remains controversial. Therefore, we aimed to assess the value of emphysema extent on computed tomography (CT) on the diagnosis of persistent airflow limitation. Furthermore, we developed a diagnostic criterion for further verification.Materials and methodsWe retrospectively enrolled patients who underwent chest CT and lung function test. To be specific, 671 patients were enrolled in the derivation group (Group 1.1), while 479 patients were in the internal validation group (Group 1.2). The percentage of lung volume occupied by low attenuation areas (LAA%) and the percentile of the histogram of attenuation values were calculated.ResultsIn patients with persistent airflow limitation, the LAA% was higher and the percentile of the histogram of attenuation values was lower, compared with patients without persistent airflow limitation. Using LAA% with a threshold of −950 HU >1.4% as the criterion, the sensitivity was 44.3% and 47.2%, and the specificity was 95.2% and 95.7%, in Group 1.1 and Group 1.2, respectively. The specificity was influenced by the coexistence of interstitial lung disease, pneumothorax, and post-surgery, rather than the coexistence of pneumonia, nodule, or mass. Multivariable models were also developed.ConclusionThe emphysema extent on CT is a highly specific marker in the diagnosis of persistent airflow limitation.

The Normal Lung Index From Quantitative Computed Tomography for the Evaluation of Obstructive and Restrictive Lung Disease

“…Moreover, QCT parameters are mostly semiautomated or fully automated, can be used for comparison over time without being limited by interobserver variations, and are suitable to patients who have some contraindication or are unable to perform spirometry 6,15,33. It facilitates reliable clinical staging of pulmonary parenchymal diseases and can be used for the prediction of mortality as demonstrated in other studies in the literature 7,9,32,34–37. Both Haruna et al7 and Johannessen et al31 have shown that the extent of emphysema assessed by QTC were significant predictors of mortality in patients with COPD.…”

“…6,15,33 It facilitates reliable clinical staging of pulmonary parenchymal diseases and can be used for the prediction of mortality as demonstrated in other studies in the literature. 7,9,32,[34][35][36][37] Both Haruna et al 7 and Johannessen et al 31 have shown that the extent of emphysema assessed by QTC were significant predictors of mortality in patients with COPD. Regarding ILD, other parameters such as kurtosis, skewness, and different analysis of lung densities or texture have also been reported as predictors of mortality in this population.…”

Emphysema Quantification and Severity Classification with 3-Dimensional Averaging Kernel and Airways Removal

“…One commonly utilized method for emphysema quantification based on CT imaging is to measure the percentage of voxel-wise low attenuation area (LAA). Previous attempts on emphysema quantification have determined the −950 HU threshold to be optimal or at least near-optimal for voxel-wise LAA classification (9), and LAA scores with the −950 threshold were used in pulmonary function related predictions such as airflow limitation (10). Traditional single voxel-wise LAA is a suboptimal metric for emphysema evaluation because it fails to exclude regions of single voxel LAA that can be physiologically present in patients with normal lung physiology and could be accentuated by quantum mottles especially in low dose chest CTs (11).…”