Abstract
Asthma is a chronic airway inflammatory disorder. Nitric oxide (NO) is non-invasively measured in exhaled breath (FeNO). The aim of the study was to investigate the anthropometric and physiologic factors that influence FeNO measurements. Also, to evaluate FeNO correlation with spirometry and inflammatory markers in asthma and rhinitis. The study was a prospective analysis of asthma (BA) and rhinitis (AR) in patients enrolled from outpatient clinics between 2011 and 2015. Healthy controls (HC) were enrolled from the community. All subjects underwent baseline spirometry with reversibility, FeNO measurements, skin prick tests, and blood sampling for absolute eosinophil counts and serum total IgE levels. Of 528 enrolled participants, 215 were BA, 248 were BA-AR and 65 were HC. The mean FeNO was higher in atopic versus nonatopic subjects (34.14 vs. 25.99; p < 0.001); asthmatics versus non-asthmatics (30.46 vs. 12.91; p < 0.001), and in participants with BA-AR, compared to those without BA-AR (32.56 vs. 30.46; p < 0.001). The odds ratio for FeNO in the study population showed a significant positive association with male gender, absolute eosinophil count (AEC), breathlessness, duration of symptoms, family history and atopy. In examining the diagnostic accuracy of FeNO for asthma, the AUC for FeNO value is 0.833 (95% confidence interval [CI], 0.717-0.901), with cut-off levels to screen for asthma being 19.45 at 71.2% sensitivity and 81.8% specificity (p < 0.001). The Positive Predictive Value 96.84% (95% CI: 94.43-98.23) and Negative Predictive Value 30% (95% CI: 23.78-37.05) for asthma prediction with FeNO. The study highlights the importance of estimation of anthropometric parameters and dyspnea assessment in the evaluation of FeNO levels. Also, the presence of atopy may influence the results in the interpretation of FeNO readings. Moreover, the study have demonstrated that spirometry and FeNO have no significant correlation, which further lays emphasis on them as being different physiological parameters of asthma.  .
Highlights
Asthma is a chronic airway inflammatory disorder
The mean FeNO was higher in atopic than in non-atopic patients (34.14 vs. 25.99; p < 0.001), higher in asthmatics than in non-asthmatics (30.46 vs. 12.91; p < 0.001) and higher in participants with allergic rhinitis compared with those without this disorder (32.56 vs. 30.46; p < 0.001)
Men have consistently higher FeNO levels as compared to women [5]; even the present study reports higher FeNO levels in men
Summary
Nitric oxide (NO) is non-invasively measured in exhaled breath (FeNO). The aim of the study was to investigate the anthropometric and physiologic factors that influence FeNO measurements. To evaluate FeNO correlation with spirometry and inflammatory markers in asthma and rhinitis. Conclusion: The study highlights the importance of estimation of anthropometric parameters and dyspnea assessment in the evaluation of FeNO levels. The study have demonstrated that spirometry and FeNO have no significant correlation, which further lays emphasis on them as being different physiological parameters of asthma. NO is non-invasively measured in exhaled breath (FeNO) and has gained substantial, clinical, and scientific interest for diagnosis, monitoring, or predicting the response to the treatment of airway inflammation in asthma [5]. Allergic rhinitis patients have increased FeNO levels, reflecting the extension of
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