Influence of age and disease severity on high resolution CT lung densitometry in asthma

Background-Low attenuation areas (LAA) on computed tomographic (CT) scans h ave been shown to represent emphysematous changes in patients with chronic obstructive pulmonary disease (COPD). However, the significance of LAA is s till controversial in patients with asthma. This study was undertaken to as sess the usefulness of lung CT densitometry in the detection of airspace en largement in association with asthma severity. Methods-Forty five asthmatic subjects and 15 non-smoking controls were stud ied to determine the influence of age, pulmonary function, and asthma sever ity on mean lung density (MLD) and the relative area of the lung showing at tenuation values less than -950 HU (RA(950)) on high resolution CT (HRCT) s cans. Results-In asthmatic patients both MLD and RA(950) correlated with paramete rs of airflow limitation (%FEV1, FEV1/FVC, %FEF25-75) and lung volume (%TLC , %FRC, %RV), but not with lung transfer factor (%TLco, %TLco/VA). The resu lts of HRCT lung densitometry also correlated with patient age and severity of asthma. Conclusions-Decreased CT lung density in non-smoking asthmatics is related to airflow limitation, hyperinflation and aging, but not with lung transfer factor.