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

Abstract

Ting Cheng,1–3 Yong Li,1,3 Shuai Pang,1 Huan Ying Wan,1,3 Guo Chao Shi,3,4 Qi Jian Cheng,1,3 Qing Yun Li,3,4 Zi Lai Pan,5 Shao Guang Huang3,4 1Department of Respiratory Medicine, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai, China; 2School of Public Health, Fudan University, Shanghai, China; 3Institute of Respiratory Diseases, Shanghai Jiao Tong University School of Medicine, Shanghai, China; 4Department of Respiratory Medicine, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; 5Department of Radiology, Ruijin Hospital North, Shanghai Jiao Tong University School of Medicine, Shanghai, China Objective: The 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 methods: We 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.Results: In 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.Conclusion: The emphysema extent on CT is a highly specific marker in the diagnosis of persistent airflow limitation. Keywords: computed tomography, lung function test, emphysema, persistent airflow limitatio