Pretreatment Alveolar Nitric Oxide Levels Predict Improvement of Pulmonary Function 1 Year Following Anti-Asthma Treatments in Patients with Inhaled Corticosteroid-Naïve Asthma

Abstract

<b><i>Introduction:</i></b> Inhaled corticosteroids (ICS) are fundamental agents to subside airway inflammation and improve forced expiratory volume in 1 s (FEV₁) among asthmatics. Alveolar concentrations of nitric oxide (CANO), as well as the classical fraction of exhaled nitric oxide (FeNO50), are associated with the pathophysiology of asthma. However, the association between pretreatment CANO levels and response to anti-asthma treatments, including ICS, remains unknown. <b><i>Methods:</i></b> We retrospectively analyzed 107 patients newly diagnosed with asthma. ICS in combination with long-acting β₂-agonists (ICS/LABA) was initiated. FEV₁ and FeNO levels were evaluated at diagnosis and were followed up at 6 and 12 months after the treatment intervention. CANO levels were estimated using various expiratory flows of FeNO measurements. Factors associated with annual changes in FEV₁ (ΔFEV₁) were analyzed. Patients with a ΔFEV₁ &#x3c;–20 mL were defined as “poor-responders.” <b><i>Results:</i></b> FEV₁, FeNO50, and CANO levels significantly improved by anti-asthma treatments. The average ΔFEV₁ was 85 (176) mL. Eighty-two patients continuously took ICS/LABA treatment. Higher pretreatment CANO levels and continuous use of LABA were independent predictive factors for the improvement of FEV₁ on multivariate analysis. The decline in FeNO50 and CANO levels by the anti-asthma treatments was significantly greater in 81 responders than in 26 poor-responders. CANO, but not FeNO50, levels at 12 months were significantly higher in poor-responders than in responders (<i>p</i> = 0.009). <b><i>Conclusion:</i></b> Levels of CANO, but not FeNO50, predict changes in pulmonary function in ICS-naïve asthmatics. Meanwhile, persistently high levels of CANO may be related to poor responsiveness to treatments assessed by ΔFEV₁.