The Diagnostic Value of the Fractional Exhaled Nitric Oxide for Asthma

Objective To determine the diagnostic value of fractional exhaled nitric(FeNO) measurement in diagnosis of bronchial asthma.Methods The patients with unkown-cause respiratory symptoms including wheezing,cough,and breathlessness were enrolled from August to September in 2008.FeNO was measured by nitric oxide analyzer(NIOX;Aerocrine AB;Solna,Sweden).Bronchial challenge test(BCT) or bronchodilator test was defined as golden standard for asthma diagnosis.The value of FeNO was assessed and the optimal operating point of FeNO testing was determined by the means of the receiver operating characteristic(ROC) curves.Results A total of 101 patients were enrolled,in which 48 cases were diagnosed as asthma by positive yield in BCT(in 38 cases) or bronchodilator test(in 10 cases).The severity of airway hyperresponsiveness(AHR) judged by BCT was mild in 15 cases,moderate in 15 cases and severe in 8 cases.The levels of FeNO of asthma group were higher than those of non-asthma group [(68.19±43.00)ppb vs(19.52±10.60)ppb,P0.05].A linear correlation of FeNO with lnPD20FEV1 was revealed in the cases with AHR.Area under ROC curve was 0.9.The optimal diagnostic cutoff point was 36.5 ppb which was capable of differentiating asthma and non-asthma with sensitivity of 92.7%,specificity of 83.3%,positive predictive value of 79.17%,negative predictive value of 94.34% and accuracy of 87.13%.Conclusion FeNO test may be helpful in the diagnosis of asthma with high sensitivity and specificity.