[The methodological aspects of nasal and exhaled nitric oxide levels in adult Japanese asthmatics].

BACKGROUND: Because both allergic rhinitis and asthma are caused by eosinophilic airway inflammation, using the same method to measure the eosinophilic inflammation of both the upper and lower airway would be advantageous. The levels of nitric oxide in exhaled air (FeNO) and nasal air (nNO) are useful as noninvasive markers of eosinophilic airway inflammation. Although the off-line method of measuring these parameters is easier and more useful than the on-line method, studies using the off-line method are rare in Japan.

METHODS: In Study 1, we measured the levels of nNO and FeNO in 9 healthy controls and 9 subjects with allergic rhinitis, to validate the methodology for using the off-line method to measure nNO. In Study 2, we measured the nNO and FeNO levels of and performed spirometry on 69 stable asthmatics treated with inhaled corticosteroid.

RESULTS: In Study 1, nNO levels were significantly increased in patients with allergic rhinitis compared with healthy subjects (31.0 [20.8 to 41.2] versus 7.4 [0.0 to 14.8] ppb {median [95% confidence interval]}, p=0.018). The 69 patients with asthma that comprised the study population in Study 2 were classified as asthmatics with rhinitis (treatment-naïve, n=14; treated with antiallergic drugs, n=11; treated with intranasal corticosteroid, n=19) and asthmatics without rhinitis (n=15). Although FeNO did not differ among groups, nNO was significantly increased in treatment-naïve asthmatics with rhinitis compared with patients with asthma only (26.5 [17.1 to 35.9] versus 8.0 [-1.1 to 17.1] ppb, p=0.033).

CONCLUSION: nNO levels measured by the off-line method are useful markers of allergic rhinitis.