Emphysema subtypes and Preserved Ratio Impaired Spirometry in smokers

Abstract

<b>Background:</b> Emphysema and its subtypes such as centrilobular and paraseptal emphysema (CLE and PSE) have been addressed in smokers with chronic obstructive pulmonary disease. However, little is known about the prevalence and clinical impacts of emphysema subtypes in smokers with Preserved Ratio Impaired Spirometry (PRISm). <b>Methods:</b> This multicenter cross-sectional study included Japanese smokers at age of ≥40 years with ≥ 10 pack-years smoking history. CLE and PSE were visually identified on full-inspiratory CT based on the Fleischner Society classification system. Air-trapping was assessed as a ratio of FVC to total lung capacity measured on CT (FVC/TLC_CT). <b>Results:</b> Total 546 smokers were enrolled and classified into those with normal spirometry (n=291), PRISm (n=71) and COPD (GOLD spirometric stage I/II/III/IV= 54/79/40/11). The PRISm group included more women and showed lower FVC, TLC_CT than the normal spirometry and COPD groups while body mass index was comparable to the normal spirometry and COPD groups. Air-trapping was the greatest in the COPD group, followed in order by PRISm and normal spirometry. The prevalence of PSE and CLE in the PRISm group (37% and 30%, respectively) was lower than in the COPD group. In multivariable analysis, CLE but not PSE in the PRISm group was associated with lower FVC/TLC_CT independent of demographic factors. <b>Conclusion:</b> Approximately 30-40% smokers with PRISm showed PSE and/or CLE, and the presence of CLE was associated with increased air-trapping. Whether emphysema subtyping helps improve clinical managements of smokers with PRISm should be further investigated in longitudinal studies.