Can nasal nitric oxide be a biomarker to differentiate allergic and non-allergic rhinitis?

Abstract

Abstract Background Nasal nitric oxide (nNO), a noninvasive indicator for eosinophilic airway inflammation, has not been adequately studied in different types of rhinitis. The aim of this study was to compare nNO levels between allergic (AR) and non-allergic rhinitis (NAR). Patients were included based on their chronic nasal symptoms. Total nasal symptoms score (TNSS) were evaluated. nNO was measured transnasally with a flow of 5 ml/s from the nostril with an NO analyzer (NIOX MINO; Aerocrine, Sweden). Results were evaluated as parts per billion (ppb). Results Four hundred forty-three patients (277 F/166 M)—337 with AR (76%) and 106 with NAR (24%)—were assessed. Patients with AR had significantly higher TNSS, more severe disease, and longer duration of disease compared to NAR group. Allergic rhinitis had significantly higher nNO levels than NAR (370 ppb vs 290 ppb) (p = 0.001). Likewise, significant differences were observed in female gender, in patients with BMI ≥ 25 kg/m2 and those without sinusitis between the two groups. When nNO were further evaluated in comorbid asthma, patients with AR w/o asthma had the highest TNSS and had significantly higher nNO level (p < 0.001). NAR+A group, with the longest duration of rhinitis, was significantly older and had the lowest nNO level (p < 0.001). Conclusions This study showed that nNO levels were significantly higher in AR patients than NAR. Although there is no recommended standard threshold for nNO, this study confirmed the utility of nNO in differentiating AR and NAR in addition to its known fast and non-invasive advantages.