Diagnostic Significance Of Exhaled Nitric Oxide And Serum Total IgE In Cough Variant Asthma

Aims: Bronchial asthma is a kind of heterogeneous disease which is involving a variety of cells,such as eosinophils,neutrophils,mast cells,T lymphocytes,etc.The dominating clinical manifestations include recurrent wheezing,shortness of breath,chest tightness and cough.Excluding typical symptoms,there are also atypical asthma symptoms without wheezing symptoms and wheezing signs,such as cough variant asthma and chest tightness variant asthma,among which cough variant asthma(CVA)is more common.CVA is based on cough as the only or main symptoms,no asthma,shortness of breath and other typical symptoms and signs of asthma,diagnosis of the disease needs to improve lung function and other related examinations as well as to eliminate the chronic cough caused by other diseases.In view of pathogeny,diagnosis and treatment,chronic cough could be distinguished into several varieties: cough variant asthma(CVA);eosinophilic bronchitis(EB);upper airway cough syndrome(UACS);eosinophilic gastroesophageal reflux cough(GERC);allergic cough(allergic cough),etc.Beyond the above causes,pulmonary interstitial fibrosis;bronchial lung cancer and chronic obstructive pulmonary disease can also lead to chronic cough,even angiotensin-converting enzyme inhibitors or other drugs can cause drug-induced cough,and there are still some unknown reasons.Although the common manifestation of chronic cough with different causes is coughing over 8 weeks,the pathogenesis,pathophysiological process,other clinical manifestations and physicochemical examination results of different diseases may bedifferent.Different physicochemical results have quite important significance for the diagnosis of chronic cough.This study aimed to discuss the clinical value of exhaled nitric oxide(FeNO),eosinophil count and serum total IgE measurement in the diagnosis of cough variant asthma(CVA)by analyzing the clinical data of patients with cough variant asthma and other chronic cough in our department.Objectives and Methods: Collected the information of chronic cough patients with cough for more than 8 weeks who visited the outpatient department of our hospital from May 2016 to December 2017.According to the diagnosis results,they were divided into cough variant asthma patients(61 cases)and other chronic cough patients(47 cases).The former was defined as CVA group and the latter as control group.Collected the data of general characteristics(including age,gender,etc.)of the two groups,and the results of perfect FeNO test,serum total IgE test,blood routine,pulmonary function test,bronchodilation test(BDT)or bronchial provocation test(BPT)to summarize,count and analyze.SPSS 22.0 statistical software was used for data analyzing.Wherein,if the measurement data were normally distributed,it was expressed as mean standard deviation,using t test to make comparison,whereas,those not conformed to normal distribution were expressed by median(four directions)and compared by rank sum test.According to the results of FeNO test and serum total IgE test,the optimum diagnostic threshold,the corresponding sensitivity and specificity were obtained,whereupon,the corresponding positive predictive value(PPV)and negative predictive value(NPV)could be calculated.Depict ROC curves of both FeNO detection and serum total IgE detection respectively by using(1-specificity)as abscissa and sensitivity as ordinate.Pearson correlation analysis was used to analyze whether FeNO test was correlated with blood routine,serum total IgE test and lung function test.The statistical results were all bounded by P < 0.05,which represented a significant difference.Results: According to the result,it showed no prominent distinction in the aspects of age or gender between CVA group and control group.Compared with the control group,the indexes of CVA group and control group were expressed as mean standarddeviation.The detection of FeNO in CVA group was(87.23+53.91),the data in control group was(26.11±19.92),(t=8.162,P<0.01).The serum total IgE detection level in CVA group was(224.89 +205.38)and in control group was(117.42±170.57),(t=2.969,P < 0.01).Both of these tests’ differences were statistically significant.The median FeNO test and serum total IgE test were compared between the two groups.The median FeNO test was 77 PPD in the CVA group and 21 PPD in the control group,and the median of serum total IgE detection in the CVA group was 129.620IU/ml,in the control group,the figure was 45.560IU/ml.In the diagnosis of CVA,the optimal critical value of FeNO detection was 32.50ppb(area under ROC curve was 0.890),and the optimal critical value of serum total IgE detection was 70.545 IU/ml(area under ROC curve was 0.703).The accuracy of serum total IgE diagnosis test was lower than that of FeNO test.To compare the sensitivity,specificity,PPV and NPV of FeNO and serum total IgE test as well as the combined results.The sensitivities were 88.5%,75.4% and 68.9%respectively.The specificities were 80.9%,59.6% and 89.4% respectively.The positive predictive values were 85.7%,70.7% and 89.4% respectively.The negative predictive values were 84.4%,65.1% and68.9% respectively.Statistical analysis showed that there was no significant difference in sensitivity and specificity between the two tests in the separate test,but the combined detection could greatly improve specificity,which was more valuable for the diagnosis of CVA.To make correlative analysis of clinical application among FeNO detection and blood routine,serum total IgE determination and pulmonary function examination.It was found that there were positive correlations between FeNO and serum eosinophil count(EOS).Conclusions: There were significant differences in the mean and standard deviation between the two groups in the detection of FeNO and serum total IgE.The optimum critical value of FeNO in the diagnosis of CVA was 32.50 ppb.When FeNO was over 32.5 ppb,it could be used as a positive test result.FeNO detection and serum total IgE detection had certain diagnostic value in the diagnosis of CVA,while jointdetection was more significant and more valuable for diagnosis.In this study,we found that serum eosinophil(EOS)count of CVA group was positively correlated with the detection of FeNO,serum EOS count and FeNO value increased accordingly.