Low-dose Volumetric Computed Tomography for Quantification of Emphysema in Asymptomatic Smokers Participating in an Early Lung Cancer Detection Trial

PURPOSE: High-resolution computed tomography (CT) is a validated method to quantify the extent of pulmonary emphysema. In this study, we assessed the reliability of low-dose volumetric CT (LDCT) for the quantification of emphysema and its correlation with spirometric indices of airway obstruction. MATERIALS AND METHODS: The study population consisted of 102 consecutive current and former smokers participating in a lung cancer screening trial. All subjects underwent spirometry testing and LDCT at entry and a LDCT after 12 months. The extent of emphysema was estimated by 2 techniques; by using the lung attenuation threshold analysis and by visual assessment of the 2 independent radiologists. The reproducibility of these determinations was assessed using test-retest reliability and kappa coefficient of agreement. The correlation of LDCT-based emphysema determinations with indices of airway obstruction on spirometry was also calculated. RESULTS: Eighty percent of the participants were male, with a mean (standard deviation) age of 54.5 (7.5) years, and median pack-years (interquartile range) of 20 (24). Test-retest reliability of all LDCT-based emphysema determinations was very good (intraclass correlation coefficient of 0.92 for the volume of emphysema, and 0.93 for the emphysema index or emphysema volume/total lung volume). Similarly, there was an excellent interrater agreement for visual assessment of emphysema (kappa coefficient=0.91). Higher volumes of emphysema measured quantitatively or visually significantly correlated with spirometric markers of airway obstruction. CONCLUSIONS: Volumetric LDCT is a reliable and valid technique for the quantification of emphysema in asymptomatic smokers.