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

¹ Dept of Pulmonology, Medisch Spectrum Twente, The Netherlands
² Dept of Pulmonology, Medical Center Leeuwarden, The Netherlands
³ Dept of Pulmonology, Leiden University Medical Center, The Netherlands; and Dept of Respiratory Medicine, Academic Medical Center, Amsterdam, The Netherlands
⁴ Dept of Medical Decision Making, Leiden University Medical Center, The Netherlands
⁵ Dept of Pulmonology, Leiden University Medical Center, The Netherlands
⁶ Dept of Respiratory Medicine, Academic Medical Center, Amsterdam, The Netherlands

^* To whom correspondence should be addressed. E-mail: h.vanveen{at}ziekenhuis-mst.nl.

	Abstract

A subset of patients with asthma has progressive loss of lung function despite treatment with corticosteroids. The aim of this study was to identify risk factors of decline in FEV₁ in patients with difficult-to-treat asthma.

136 non-smoking patients with difficult-to-treat asthma were recruited in 1998–1999, and follow-up assessment was performed 5–6 years later in 98 patients. We analyzed the predictive effect of clinical characteristics and inflammatory markers at baseline (asthma onset and duration, atopy, airway hyperresponsiveness, blood and sputum eosinophils and the fraction of exhaled nitric oxide (FE_NO)) on subsequent decline in postbronchodilator FEV₁.

Patients with high FE_NO (20 ppb) had an excess decline of 40.3 ml·yr^-1 ((CI):7.3 to 73.2) as compared to patients with low FE_NO. FE_NO 20 ppb was associated with a 1.9-fold (CI:1.1 to 2.6) increased risk of having an accelerated decline in FEV₁ (25 ml·yr^-1). In patients with baseline FEV₁ 80% of predicted this relationship was even stronger: 90% vs. 29% had accelerated decline in FEV₁ (FE_NO 20 ppb vs. FE_NO <20 ppb resp., relative risk 3.1 (CI:1.7 to 3.4)).

FE_NO is a predictor of accelerated decline in lung function in patients with difficult-to-treat asthma, particularly if FEV₁ is still normal.

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