Exhaled nitric oxide as a diagnostic test for asthma in rhinitic patients with asthmatic symptoms

Background: Rhinitis is a major risk factor for asthma, so that evaluation of the lower airways is recommended in patients with rhinitis. Exhaled nitric oxide (FENO) is considered a marker of airway inflammation and it has been found to be useful for the screening of patients with suspected diagnosis of asthma. Our aim was to assess the validity and accuracy of FENO to identify patients with asthma in 48 non-smoking patients with persistent rhinitis and asthma-like symptoms. Methods: Asthma was diagnosed on the basis of 12% improvement in FEV1 after salbutamol or a methocholine PD20FEV1 < 800 mu g. Prior to lung function FENO was measured with the single exhalation method at 50 ml/s. Results: The geometric mean (95% confidence interval) FENO was significantly higher in the 18/48 asthmatics than in the non-asthmatic patients (60ppb, Cl 95%: 50-89, versus 30 ppb, Cl 95%: 28-45, P = 0.001). Receiver operating characteristic (ROC) curve for the diagnosis of asthma indicated that FENO is an acceptable discriminator between patients with and without asthma (area under the ROC curve = 0.78). None of the asthmatic patients had FENO values < 25ppb and all the patients with FENO > 100 ppb (n = 5) were asthmatics. The sensitivity and specificity of FENO for detecting asthma, using 36 ppb as cut-off point, were 78% and 60% and the positive and negative predictive values were 54% and 82%, respectively. Conclusions: Measuring FENO may be useful for the screening of rhinitic patients with asthma-like symptoms. (c) 2006 Elsevier Ltd. All rights reserved.