The Diagnostic Value Of Airway Three-dimensional CT Quantitative Parameters In Patients With Chronic Obstructive Pulmonary Disease

ObjectiveChronic Obstructive Pulmonary Disease（COPD）is a disease characterized by persistent respiratory symptoms and restricted airflow,which is caused by abnormal airway and/or alveoli exposed to toxic particles or gases.Acute exacerbations and repeated hospitalizations in patients with COPD make it the third leading cause of death worldwide.As the standard of diagnosis and clinical classification,pulmonary function test（PFT）is easily influenced by many factors,such as patient’s age and cooperation,severity of disease or comorbidities,and less sensitive for early patients with no obvious symptoms.The purpose of this study was to explore the diagnostic value of CT parameters,especially the correlation between small airway parameters and lung function in patients with early COPD.MethodsA total of 129 COPD patients in acute exacerbation and 32 healthy subjects in the same period were prospectively enrolled from January 2020 to October 2021 in the First Affiliated Hospital of Anhui Medical University and Lu ’an Shili Hospital.The age（years）,gender,body mass index（BMI）（kg/m2）,smoking pack year,St George’s questionnaire（SGRQ）score,chronic obstructive pulmonary disease assessment（CAT）score,modified British medical research council（mMRC）index,BODE index and sixminute walk distance（6MWT）of subjects were collected.Each subject underwent CT scans and lung function tests.After three-dimensional reconstruction of CT images,software was used to calculate the percentage of emphysema（LAA%）,the ratio of pulmonary artery to aorta（PA:A）and airway dimensions of the apical bronchus and the posterior basal bronchus of the right lower lung from the third to the eighth generations.According to the classification of GOLD（Global Initiative for Chronic Obstructive Lung Disease）,COPD patients were divided into GOLD 1～2（45 cases）and GOLD3～4（84 cases）.The difference of groups was analyzed using one-way ANOVA or KruskalWallis H Test.The correlation of CT parameters and pulmonary function or clinical indicators was analyzed by Spearman’s correlation,and the predictors of PFT was selected by Multiple linear regression analysis.The diagnostic value of quantitative CT parameters for COPD was evaluated using ROC curve.Results1.Whole lung LAA%-950HU in GOLD 1～2 group was lower than that control group and GOLD3～4 group（all adjusted P<0.001）,and whole lung LAA%-950HU in GOLD3～4 group was higher than control group（adjusted P<0.001）.WA%7～8 in patient with COPD was higher than control group（adjusted P<0.001）,and WA%7～8 in GOLD3～4 group was higher than GOLD1-2 group（adjusted P=0.019）.TDR7～8 in patient with COPD was higher than control group（all adjusted P<0.001）.PA:A in patient with COPD was higher than control group（all adjusted P<0.001）and PA:A of GOLD3-4 group was higher than GOLD 1-2 group（adjusted P<0.001）.2.There was significant negative correlation between LAA%-950HU of each lobe and FEVl/FVC,FEVl%pre,FVC%pre,FEF50%and FEF75%in patients with COPD（all P<0.001）;LAA%-950HU had the highest correlation with FEF75%（r=-0.588,P<0.001）.Comparing the LAA%-950HU of each lobe,the LAA%-950HU of lower lobe in both lungs had the highest correlation with lung function.3.Whole lung LAA%-950HU and TDR7～8 could jointly predict the change of FEVl/FVC by 45.2%in patients with COPD,whole lung LAA%-950HU negatively predicted FEVl/FVC（standardized β=-0.634,P<0.001）,and TDR7～8 negatively predicted FEVi/FVC（standardized β=-0.258,p<0.001）.Similarly,whole lung LAA%-950HU and TDR7～8 could jointly predict the change of FEVi%pre by 34.8%in COPD patients,whole lung LAA%950HU negatively predicted FEVi%pre（standardized β=-0.520,p<0.001）,and TDR7～8 negatively predicted FEVi%pre（standardized β=-0.290,p<0.001）.4.The ROC curve of quantitative CT parameters in diagnosing COPD showed that the AUC of TDR7～8 was 0.722,the cut-off point was 29.7,the sensitivity was 72%,and the specificity was 72%（p<0.001）while AUC of whole lung LAA%-950HU was 0.516,the cutoff point was 1.3%,the sensitivity was 29%,and the specificity was 91%（p=0.019）.ConclusionBy using the chest CT three-dimensional reconstruction and quantitative analysis in patients with COPD,we found that small airway quantitative parameters TDR7～8 and whole lung LAA%-950HU were negatively correlated with lung function separately,which could jointly predict the decrease of FEVl/FVC and FEVl%Pre.It is showed that TDR7～8 and whole lung LAA%-950HU can better evaluate and predict the decline of pulmonary function in COPD patients.Comparing the CT quantitative parameters between healthy control group and COPD patients,we found that the percentage of wall area and the wall thickness to diameter ratio in small airway increased in the early stage of COPD,while emphysema and PA:A and PA:A increased significantly in severe COPD,which suggested that small airway disease is predominant in early COPD and the destruction of emphysema and the widening of pulmonary artery occurred later.At the same time,the sensitivity and specificity of small airway parameters TDR7～8 were both 72%,indicating that small airway parameters could be used to assist the diagnosis and early recognition of COPD,quantitative small airway parameters using three-dimensional reconstruction can provide certain help for the clinical diagnosis and evaluation of COPD.