Objectives/Hypothesis: The aim of this study was to evaluate the associations between nasal nitric oxide and nasal

symptoms, sinus opacification, and markers of allergic inflammation in allergic and in nonallergic rhinitis while taking into

account the effect of sinus obstruction.

Study Design: We studied 175 young adult subjects divided into three groups: 1) allergic rhinitis, 2) nonallergic rhinitis,

and 3) controls.

Methods: We measured nasal nitric oxide using the breath-holding method and exhaled nitric oxide and scored semiquantitatively

nasal computed tomography scans for opacification and obstruction. We also assessed the visual analogue

scores of nasal symptoms, eosinophil count, and interleukin-13 mRNA levels in nasal biopsies.

Results: The level of nasal nitric oxide correlated with exhaled nitric oxide (r50.377, P<.001). In allergic rhinitis, nasal

nitric oxide was elevated when compared to the controls, and an inverse correlation existed between the nasal nitric oxide

level and sinus ostial obstruction (r520.272, P5.013). In nonallergic rhinitis, the level of nasal nitric oxide was similar to

that of the controls. In allergic rhinitis, nasal nitric oxide correlated positively with the opacification score (r50.250,

P5.033) and the nasal eosinophil count (r50.293, P5.030) of patients without a marked sinus ostial obstruction.

Conclusions: Sinus ostial obstruction lowers the level of nasal nitric oxide and reduces its value as an indicator of allergic

mucosal inflammation. A high nasal nitric oxide level may be a useful marker of eosinophilic inflammation in the nasal

cavity and indicate the absence of marked sinus ostial obstruction.