| Background and Purpose:Cough is a common symptom in respiratory outpatient department.According to the duration of cough,it can be divided into three types:acute cough,subacute cough and chronic cough.Cough variant asthma(CVA),eosinophilic bronchitis(EB),upper airway cough syndrome(UACS),gastroesophageal reflux cough(GERC)and allergic cough(AC)are the most common causes of chronic cough.Previous studies have shown that the evaluation of airway inflammation,especially eosinophil(Eos)airway inflammation,has important guiding significance for the diagnosis and treatment of subacute and chronic cough.Exhaled nitric oxide(FeNO)and induced sputum cell classification and counting are widely used non-invasive methods to detect airway inflammation.Multiple studies have shown that FeNO is significantly correlated with eosinophilic airway inflammation and is an important marker of eosinophilic airway inflammation.Our previous small sample study suggested that FeNO levels were similar in subacute cough and chronic cough.This study aimed to expand the sample size and explore the following scientific issues:1)to clarify the differences between FeNO levels;2)To clarify the significance of FeNO in evaluating eosinophilic airway inflammation;3)To find the factors affecting FeNO level and its value in evaluating airway inflammation.To guide the clinical diagnosis and treatment of patients with subacute and chronic cough.Methods:Patients with subacute and chronic cough who were admitted to the outpatient Department of Respiratory and Critical Care Medicine,Nanfang Hospital,Southern Medical University from October 2016 to October 2021 were included.A total of 868,general data such as gender,age,weight,height,smoking history and allergy history were collected.To improve FeNO and induced sputum examination.SPSS 24.0 statistical software was used to analyze the clinical data of the patients.Measurement data conforming to normal distribution were expressed as mean ± standard deviation(X±SD),measurement data not conforming to normal distribution were expressed as median(first quartile,third quartile).Categorical count data were represented by N(%).Spearman correlation analysis was used to investigate the correlation between the two variables.The receiver operating characteristic(ROC)curve was used to evaluate the predictive value of FeNO for significant improvement of pulmonary function.P<0.05 indicated statistical significance.Results:1.There was no significant difference in FeNO level and the proportion of induced sputum Eos between subacute cough group(119 cases)and chronic cough group(749 cases)(all P>0.05).In the chronic cough group,the proportion of female patients in the normal FeNO level group was higher than that in the increased FeNO level group(64.2%vs 44.7%,P=0.001),and the proportion of smokers was lower(11.5%vs 20.6%,P=0.004).The proportion of patients with eosinophilic airway inflammation(induced sputum Eos%≥2.5%)was significantly higher in the FeNO level group than in the normal group(31.2%vs 13.5%,P<0.001).There were no significant differences in gender ratio and smoking history in subacute cough group(all P>0.05).The proportion of patients with Eos airway inflammation in FeNO increased group was significantly higher than that in normal group(34.7%vs 12.9%,P=0.05).2.According to further grouping analysis of FeNO increased group,low FeNO level group(FeNO<25 ppb)had lower sputum Eos level(0[0-1]vs 0[0-2]vs 0[2-12],P<0.001).The level of macrophages was higher(41.5±28.1 vs 37.3±25.4 vs 31.5±26.5,P<0.001).The proportion of patients with eosinophilic airway inflammation was significantly higher in the high FeNO level group(FeNO≥50ppb)(13.4%vs 20.9%vs 44.9%,P<0.001).Cox regression analysis was performed to analyze the relationship between eosinophilic airway inflammation and clinical characteristics in patients with global cough.Increased FeNO level(FeNO≥25ppb)was an independent predictor of eosinophilic airway inflammation(HR=14.978,P<0.001),especially in patients with chronic cough.FeNO≥25ppb could also be used as an independent predictor of eosinophilic airway inflammation(HR=10.607,P<0.001).3.FeNO values were higher in the atopic group than in the non-atopic group(20[12,51.75]vs 18[11,31],P=0.020).In the ROC analysis of FeNO in predicting the induction of Eos,the AUC of atopic patients as a whole was 0.700(95%CI,0.5780.822),and that of non-atopic patients was 0.706(95%CI,0.658-0.754).There was no significant difference in the predictive effect of FeNO on AUC between the two groups(P=0.99).In chronic cough,the AUC value of atopic patients was 0.682(95%CI:0.533-0.831),and that of non-atopic patients was 0.693(95%CI:0.6410.745).There was statistically significant difference in the predictive effect of FeNO on AUC between the two groups(P<0.05).Overall,the optimal cutoff value for FeNO prediction of eosinophilic airway inflammation was 27.5 PPB,which was significantly higher in atopic patients than in non-atopic patients(72 ppb vs.26.5 ppb).In chronic cough,the cut-off value of atopic patients was significantly higher than that of non-atopic patients(72 ppb vs 26.5 ppb).Further Logistic regression analysis showed that smoking(OR=1.796,95%CI:1.127-2.847,P=0.013)and allergic rhinitis(OR=2.391,95%CI:1.032-5.596,P=0.041)were the factors affecting the predictive value of FeNO.Both were associated with higher FeNO values,even after correction.Conclusions:There was no significant difference in FeNO level between patients with chronic cough and patients with subacute cough.Patients with increased FeNO levels are more likely to have eosinophilic airway inflammation.Patients with atopic history often have high levels of FeNO,and the cut-off value for predicting eosinophilic airway inflammation is 27.5 ppb.However,atopic history can attenuate the predictive effect of FeNO on sputum Eos in patients with chronic cough. |
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