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

Summary 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 (FE NO ) 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 FE NO 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 FEV 1 after salbutamol or a methocholine PD 20 FEV 1 NO was measured with the single exhalation method at 50ml/s. Results The geometric mean (95% confidence interval) FE NO was significantly higher in the 18/48 asthmatics than in the non-asthmatic patients (60ppb, CI 95%: 50–89, versus 30ppb, CI 95%: 28–45, P = 0.001 ). Receiver operating characteristic (ROC) curve for the diagnosis of asthma indicated that FE NO is an acceptable discriminator between patients with and without asthma (area under the ROC curve=0.78). None of the asthmatic patients had FE NO values NO >100ppb ( n = 5 ) were asthmatics. The sensitivity and specificity of FE NO for detecting asthma, using 36ppb as cut-off point, were 78% and 60% and the positive and negative predictive values were 54% and 82%, respectively. Conclusions Measuring FE NO may be useful for the screening of rhinitic patients with asthma-like symptoms.