Nasal nitric oxide levels do not allow for discrimination between olfactory loss due to various etiologies

Abstract

Objectives/hypothesis: Nasal nitric oxide (NO) and olfactory function are decreased in patients with chronic inflammatory sinonasal disease, suggesting a link between these two parameters. The aim of the study was to investigate nasal NO levels in patients with olfactory dysfunction due to different causes.

Study design: Prospective study in a university clinic setting (tertiary referral center).

Methods: Posttraumatic (n = 11), idiopathic (n = 13), and sinonasal-related olfactory-impaired patients (n = 55) were compared with healthy subjects (n = 11). Nasal NO levels, olfactory testing (Sniffin' Sticks), and rhinosinusitis questionnaires (Short-Form 36, Sinonasal Outcome Test 22, Rhinosinusitis Disability Index) were obtained.

Results: No significant difference in nasal NO levels were found between the different olfactory dysfunction causes. Nasal NO correlated negatively with age and positively with overall olfactory function, olfactory discrimination, and identification but not with olfactory thresholds. The more nasal symptoms prevailed in the Rhinosinusitis Disability Index, the lower the nasal NO.

Conclusions: Nasal NO levels do not allow for discrimination between olfactory loss due to various etiologies based on the present data. Nasal NO production seems to decrease with age and also seems to be associated to overall olfactory function and in particular to central nervous system tasks such as olfactory discrimination and identification but not to olfactory thresholds. These findings raise questions about the link and interaction between olfactory function and nasal NO.