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

• Published in: International journal of chronic obstructive pulmonary disease Vol. 11; no. 1; pp. 3015 - 3022
• Main Authors: Wang, Wei, Xie, Mengshuang, Dou, Shuang, Cui, Liwei, Xiao, Wei
• Format: Journal Article
• Language: English
• Published: New Zealand Dove Medical Press Limited 01.01.2016; Dove Medical Press Ltd; Dove Medical Press
• Subjects: Aged; airway collapse; Airway management; Area Under Curve; Asthma; Asthma - diagnosis; Asthma - diagnostic imaging; Asthma - physiopathology; Biological markers; Care and treatment; Case-Control Studies; CAT scans; Chronic obstructive lung disease; Chronic obstructive pulmonary disease; Clinical medicine; Computer Simulation; COPD; Cross-Sectional Studies; Diagnosis; Emphysema; Female; Health aspects; Hospitals; Humans; Lung - diagnostic imaging; Lung - physiopathology; Lung diseases; Male; Maximal Expiratory Flow-Volume Curves; Mean square errors; MEFV; Methods; Middle Aged; Multidetector Computed Tomography; Original Research; overlap; Predictive Value of Tests; Pulmonary Disease, Chronic Obstructive - diagnosis; Pulmonary Disease, Chronic Obstructive - diagnostic imaging; Pulmonary Disease, Chronic Obstructive - physiopathology; Pulmonary Emphysema - diagnosis; Pulmonary Emphysema - diagnostic imaging; Pulmonary Emphysema - physiopathology; Pulmonary Ventilation; ROC Curve; Software; Spirometry; Syndrome; United States > US; Germany; asthma; overlap; MEFV; airway collapse; COPD; emphysema
• ISSN: 1178-2005; 1176-9106; 1178-2005
• DOI: 10.2147/COPD.S118415

In a previous study, we demonstrated that asthma patients with signs of emphysema on quantitative computed tomography (CT) fulfill the diagnosis of asthma-COPD overlap syndrome (ACOS). However, quantitative CT measurements of emphysema are not routinely available for patients with chronic airway disease, which limits their application. Spirometry was a widely used examination tool in clinical settings and shows emphysema as a sharp angle in the maximum expiratory flow volume (MEFV) curve, called the "angle of collapse (AC)". The aim of this study was to investigate the value of the AC in the diagnosis of emphysema and ACOS. This study included 716 participants: 151 asthma patients, 173 COPD patients, and 392 normal control subjects. All the participants underwent pulmonary function tests. COPD and asthma patients also underwent quantitative CT measurements of emphysema. The AC was measured using computer models based on Matlab software. The value of the AC in the diagnosis of emphysema and ACOS was evaluated using receiver-operating characteristic (ROC) curve analysis. The AC of COPD patients was significantly lower than that of asthma patients and control subjects. The AC was significantly negatively correlated with emphysema index (EI; =-0.666, <0.001), and patients with high EI had a lower AC than those with low EI. The ROC curve analysis showed that the AC had higher diagnostic efficiency for high EI (area under the curve =0.876) than did other spirometry parameters. In asthma patients, using the AC ≤137° as a surrogate criterion for the diagnosis of ACOS, the sensitivity and specificity were 62.5% and 89.1%, respectively. The AC on the MEFV curve quantified by computer models correlates with the extent of emphysema. The AC may become a surrogate marker for the diagnosis of emphysema and help to diagnose ACOS.