Exhaled nitric oxide predicts lung function decline in difficult-to-treat asthma

Open Access
Publisher Website
Google Scholar
Abstract
A subset of patients with asthma is known to have progressive loss of lung function despite treatment with corticosteroids. The aim of the present study was to identify risk factors of decline in forced expiratory volume in one second (FEV1) in patients with difficult-to-treat asthma.In total, 136 nonsmoking patients with difficult-to-treat asthma were recruited between 1998 and 1999. Follow-up assessment was performed 5–6 yrs later in 98 patients. The predictive effect of clinical characteristics and inflammatory markers were analysed at baseline (asthma onset and duration, atopy, airway hyperresponsiveness, blood and sputum eosinophils, and the fraction of nitric oxide in exhaled air (FeNO)) on subsequent decline in post-bronchodilator FEV1.Patients with highFeNO(≥20 ppb) had an excess decline of 40.3 (95% confidence interval (CI) 7.3–73.2) mL·yr−1compared to patients with lowFeNO.FeNO≥20 ppb was associated with a relative risk of 1.9 (95% CI, 1.1–2.6) of having an accelerated (≥25 mL·yr−1) decline in FEV1. In patients with baseline FEV1≥80% of predicted, this relationship was even stronger: 90versus29% had accelerated decline in FEV1(FeNO≥20 ppbversusFeNO<20 ppb respectively; relative risk 3.1 (95% CI, 1.7–3.4).Exhaled nitric oxide is a predictor of accelerated decline in lung function in patients with difficult-to-treat asthma, particularly if forced expiratory volume in one second is still normal.