Quantitative computed tomography measurements of emphysema for diagnosing asthma-chronic obstructive pulmonary disease overlap syndrome

Abstract

BackgroundThe diagnostic criteria of asthma–COPD overlap syndrome (ACOS) are controversial. Emphysema is characteristic of COPD and usually does not exist in typical asthma patients. Emphysema in patients with asthma suggests the coexistence of COPD. Quantitative computed tomography (CT) allows repeated evaluation of emphysema noninvasively. We investigated the value of quantitative CT measurements of emphysema in the diagnosis of ACOS.MethodsThis study included 404 participants; 151 asthma patients, 125 COPD patients, and 128 normal control subjects. All the participants underwent pulmonary function tests and a high-resolution CT scan. Emphysema measurements were taken with an Airway Inspector software. The asthma patients were divided into high and low emphysema index (EI) groups based on the percentage of low attenuation areas less than −950 Hounsfield units. The characteristics of asthma patients with high EI were compared with those having low EI or COPD.ResultsThe normal value of percentage of low attenuation areas less than −950 Hounsfield units in Chinese aged >40 years was 2.79%±2.37%. COPD patients indicated more severe emphysema and more upper-zone-predominant distribution of emphysema than asthma patients or controls. Thirty-two (21.2%) of the 151 asthma patients had high EI. Compared with asthma patients with low EI, those with high EI were significantly older, more likely to be male, had more pack-years of smoking, had more upper-zone-predominant distribution of emphysema, and had greater airflow limitation. There were no significant differences in sex ratios, pack-years of smoking, airflow limitation, or emphysema distribution between asthma patients with high EI and COPD patients. A greater number of acute exacerbations were seen in asthma patients with high EI compared with those with low EI or COPD.ConclusionAsthma patients with high EI fulfill the features of ACOS, as described in the Global Initiative for Asthma and Global Initiative for Chronic Obstructive Lung Disease guidelines. Quantitative CT measurements of emphysema may help in diagnosing ACOS.

A morphologic study of the airway structure abnormalities in patients with asthma by high-resolution computed tomography

“…Although 3D acquisition together with automatic analysis is time saving and is widely accepted as an optimal standard, in the study of airway morphometric characteristics in patients with asthma, the main structural features were reported to be identical with those found in HRCT alone, including bronchial wall thickness and emphysema (21)(22)(23). Furthermore, 3D is more likely to be regarded as a post-processing method, because changes visualized in twodimension (2D) projections were demonstrated to correspond to the airway flow limitations well (24).…”

Diagnosis of asthma–COPD overlap: the five commandments

“…These differences can also be observed by computed tomography, which shows distinct characteristics of ACO compared to obstructive asthma or COPD [12,13]. Patients with ACO present a higher emphysema index and a greater upper zone predominant distribution of emphysema, compared with obstructive asthma [14]. These differences indicate that asthmatics with significant exposure to smoking develop a different type of chronic obstructive airflow disease (COAD) with mixed characteristics of asthma and COPD, and justify the use of the term ACO.…”

Computer quantification of “angle of collapse” on maximum expiratory flow volume curve for diagnosing asthma-COPD overlap syndrome

“…Patients with asthmatic symptoms or a history of asthma were excluded from the COPD group. On the basis of the results of our previous study, asthma patients with high EI were defined as ACOS patients 7. The asthma and COPD patients were treated in accordance with GINA and GOLD guidelines.…”

“…In our previous study, we attempted to demonstrate that asthma patients with a high emphysema index (EI) as measured by quantitative CT fulfill the characteristics of ACOS, and that quantitative CT measurements of emphysema may help in the diagnosis of ACOS 7. However, CT is not routinely available for patients with chronic airway disease, and the radiation exposure of CT restricts widespread applications.…”