Diagnostic Values Of Fractional Exhaled Nitric Oxide And Peripheral Blood Eosinophil Count In Eosinophilic Asthma

Objective:To explore the diagnostic values of fractional exhaled nitric oxide?FeNO?and peripheral blood eosinophil count in eosinophilic asthma.Methods:Retrospectively studied the clinical data of 89 patients with asthma were enrolled in the department of respiratory and critical care medicine of the First Hospital of Shanxi Medical University from May 2016 to March 2018,including 28 males and 61 females.Pulmonary function,FeNO,cytological classification of induced sputum and blood cell analysis were detected in 89 patients among them.The correlations among the FeNO,percentage of eosinophils?EOS%?in induced sputum and peripheral blood eosinophil count were pairwise compared.EOS%?3%of induced sputum was defined as eosinophilic asthma.The diagnostic efficiency and optimal thresholds points of FeNO and peripheral blood eosinophil count to diagnose eosinophilic asthma were respectively assessed by ROC curves.Results:1.There were 34 patients with eosinophilic asthma and 55 patients with non-eosinophilic asthma.There were 23 classic asthmatics both in eosinophilic asthma group and non-eosinophilic asthma group,accounting for 67.65%and 41.82%respectively,and the difference was statistically significant??²=5.613,P=0.018?.There were 10 cases of cough variant asthma in the eosinophilic asthma group and 28 cases of cough variant asthma in the non-eosinophilic asthma group,accounting for 29.41%and50.91%respectively,and the difference was statistically significant??²=3.969,P=0.046?.2.The values of FEV₁/pre?%?and FEV₁/FVC in the eosinophilic asthma group were?90.3±26.1?%and?69.1±11.8?%,respectively,which were significantly lower than those in the non-eosinophilic asthma group[?110.1±20.3?%and?80.1±6.0?%,respectively].The EOS%of induced sputum was negatively correlated with FEV₁/pre and FEV₁/FVC?r=-0.376,r=-0.448,all P<0.05?.3.There was a positive correlation between FeNO and EOS%in induced sputum?r=0.670,P<0.01?,a positive correlation between peripheral blood eosinophil count and EOS%in induced sputum?r=0.741,P<0.01?,and a positive correlation between peripheral blood eosinophil count and FeNO?r=0.647,P<0.01?.4.The optimal threshold value of FeNO was 65ppb?AUC=0.887,P<0.01?and the sensitivity was 64.7%,the specificity was 100%.The optimal threshold value of peripheral blood eosinophil count was 0.225×10⁹/L?AUC=0.898,P<0.01?,the sensitivity and specificity were 79.4%and 89.1%,respectively.The combination of FeNO and peripheral blood eosinophil count was more effective in the diagnosis of eosinophilic asthma?AUC=0.916,P<0.01?,the sensitivity was 79.4%and the specificity was 94.5%.Conclusion:1.Compared with non-eosinophilic asthma group,there were more classic asthma and less cough variant asthma in the eosinophilic asthma group,and the difference was statistically significant.2.The ventilatory function of eosinophilic asthma group was significantly lower than that of non-eosinophilic asthma group,and the EOS%of induced sputum was associated with the decrease of ventilatory function,which suggested that the decrease of ventilatory function was more significant in patients with eosinophilic airway inflammation.3.There were positive correlation among FeNO value,the EOS%of induced sputum and peripheral blood eosinophil count in asthmatic patients,which can be used as alternative markers of eosinophilic airway inflammation.4.For patients with confirmed asthma,FeNO and peripheral blood eosinophil count are reliable indicators for the diagnosis of eosinophilic asthma,and the combination of them can more effectively predict the presence of eosinophilic airway inflammation in patients with asthma.The optimal threshold value of FeNO was 65ppb?AUC=0.887,P<0.01?and the sensitivity was 64.7%,the specificity was 100%.The optimal threshold value of peripheral blood eosinophil count was 0.225×10⁹/L?AUC=0.898,P<0.01?,the sensitivity and specificity were 79.4%and 89.1%,respectively.