Exhaled nitric oxide as a diagnostic test for asthma in rhinitic patients with asthmatic symptoms
Received 21 November 2005; accepted 23 February 2006. published online 03 April 2006.
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 (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<800μg. Prior to lung function FENO was measured with the single exhalation method at 50ml/s.
Results
The geometric mean (95% confidence interval) FENO 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, ). 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>100ppb () were asthmatics. The sensitivity and specificity of FENO 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 FENO may be useful for the screening of rhinitic patients with asthma-like symptoms.
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