Fractional Exhaled Nitric Oxide: A Potential Biomarker in Allergic Rhinitis?

Background: The fractional concentration of exhaled nitric oxide (FeNO) is a surrogate biomarker for Th2-dependent bronchial inflammation. The present study investigated whether FeNO may characterize allergic rhinitis (AR) patients. Methods: A total of 553 AR patients (497 males, mean age 28.8 years) were evaluated. Those patients with a high FeNO underwent a 2-year follow-up. Results: Increased FeNO was associated with a significantly longer AR duration, impaired lung function, more severe symptoms, and more frequent bronchial hyperresponsiveness (BHR). At follow-up, 22 out of 82 patients (26.8%) with high FeNO levels (>50 ppb) developed asthma. Conclusions: AR patients may frequently have high FeNO values, exceeding 50 ppb. This might be associated with an initial impaired lung function, BHR, a perceived worsening of respiratory symptoms, and potential progression to asthma.