Nasal Fractional Exhaled Nitric Oxide, as the name suggests, measures the amount of Nitric Oxide (NO) within an airway in parts per billion and is considered a biomarker for present inflammation. Cut-off figures for diagnostic use within a clinical setting remain relatively unknown when it comes to distinguishing certain diseases from a healthy, ‘normal’ population including, Primary Ciliary Dyskinesia, Cystic Fibrosis, Allergic Rhinitis and Sinusitis. The study in review from October 2021, Study of Nasal Fractional Exhaled Nitric Oxide (FENO) in Children with Allergic Rhinitis, investigated the difference between nasal nitric oxide in healthy children verses those with symptoms of Allergic Rhinitis (AR) utilising multi-flow exhaled NO (Hypair NO, Medisoft). Inclusion criteria for AR was defined as those with one or more of the following; nasal congestion, runny nose, nasal itching or sneezing lasting > 4 days per week for 4 consecutive weeks.
Over the course of two years, 100 children (age 14yrs ±3 [6-17yrs]) partook in the study. It was found nasal NO was significantly greater in patients with allergic rhinitis (985ppb ± 232) compared to their healthy counterparts (229ppb ± 65). It was also determined that nasal peak flow (inspiratory and expiratory) were both significantly reduced in patients with AR. The authors also note a significant correlation between nasal NO, flow rates and clinical symptoms of AR. Lastly, it is clinically important to establish cut-off figures for what is considered normal vs indicative of disease, to which a nasal NO amount >794ppb was established to be most accurate through sensitivity and specificity measures.
From a clinical perspective, this study is vitally important to the ongoing work required to establish normative data and associated cut-offs needed through objective tests (nasal NO, peak flow rates) for the diagnosis of disease states when a symptomatic patient presents. As it remains early days in this research field, the use of a cut-off for allergic rhinitis >794ppb of nasal NO could be used in conjunction with clinical symptoms to determine a diagnosis in children <18yrs of age.
Link to Study: https://doi.org/10.3390/sinusitis5020013
