Cheng T, et al. - In this retrospective cross sectional study, researchers assessed the effectiveness of emphysema extent on computed tomography (CT) in diagnosing persistent airflow limitation in China and attempted to develop diagnostic criteria for further verification. Study participants included patients who underwent chest CT and lung function test. The low attenuation areas (LAA%) was higher in patients with persistent airflow limitation and the percentile of the histogram of attenuation values was lower vs patients without persistent airflow limitation. The specificity was influenced not by the coexistence of pneumonia, nodule or mass, but by the coexistence of interstitial lung disease, pneumothorax and post-surgery. Overall, it was concluded that the emphysema extent on CT is a specific marker in the diagnosis of persistent airflow limitation, which can help with COPD diagnosis.