Nasal nitric oxide(nNO) is considered a biomarker of nasal inflammation.
To perform a systematic review with meta-analysis and meta-regressions on the association between nNO levels and allergic rhinitis (AR).
PubMed, Web of Science, Scopus and EMBASE databases were systematically searched. Differences between cases and controls were expressed as standardized mean difference (SMD) with 95% confidence intervals (95%CI).
Thirty nine articles were selected: 30 containing data on nNO measured by nasal aspiration (1,881 AR patients and 1,337 controls), and 12 assessing nNO by nasal exhalation (525 AR patients and 350 controls). Compared to controls, AR presented significantly higher nNO values both during nasal aspiration (SMD: 1.309; 95%CI: 0.841, 1.777; P<0.0001) and nasal exhalation (SMD: 0.708; 95%CI: 0.303, 1.114; P=0.001). Sensitivity and subgroup analyses confirmed that the results for the evaluated outcomes were not affected by the presence of clinical confounding factors (asthma, nasal polyps, inhaled corticosteroids, smoking history), this being valid for both perennial and seasonal disease during the exposure to allergens. For the aspiration method, regression models indicated that an older age and a better pulmonary function are associated with a lower difference in nNO levels between AR patients and controls, while an increasing aspiration flow is associated with a high effect size.
nNO levels are significantly higher in chronic patients with AR, particularly when high aspiration flows are used in younger subjects, who often perceive this condition as a source of disability. Further studies are needed to define a potential role of nNO measurement in upper airway disorders.

Copyright © 2020. Published by Elsevier Inc.