Nasal levels of nitric oxide as an outcome variable in allergic upper respiratory tract disease: Influence of atopy and hayfever on nNO.

BACKGROUND: The role of nasal levels of nitric oxide (nNO) as noninvasive marker of inflammation and as an outcome variable in allergic upper respiratory tract disease has not been defined. Our aim is to determine in patients with perennial allergic rhinitis (i) whether nNO is elevated, (ii) whether increased nNO is correlated with upper respiratory tract symptoms (discrimination), and (iii) whether changes in symptom scores are associated with changes in nNO levels (responsiveness).

METHODS: Subjects (n = 38) with perennial rhinitis were studied weekly for 3 weeks. At each visit they completed a validated symptom questionnaire and had expired NO and nNO measured.

RESULTS: Nasal NO levels were higher in those allergic to house-dust mite and cat. Nasal NO levels in subjects with perennial rhinitis were not elevated compared with non-atopic asymptomatic subjects. The intra-week reproducibility of nNO measurements was poor. There was no relationship between the symptom scores and nasal NO levels (discrimination). When analysis was confined to nasal symptoms, a weak but negative correlation was identified. Changes in symptom scores from week to week were not correlated with changes in nNO levels (responsiveness).

CONCLUSIONS: Nasal NO levels were not elevated in subjects with perennial rhinitis, and nNO levels were neither discriminatory nor responsive. The measurement of nNO therefore appears not to be a useful marker of disease activity in subjects with allergic rhinitis.