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RESEARCH PRODUCT

Airway Responsiveness to Inhaled Acetaldehyde in Subjects with Allergic Rhinitis: Relationship to Methacholine Responsiveness

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<i>Background:</i> Asthmatic subjects have an exaggerated airway response to inhaled acetaldehyde, but no information is available on airway responsiveness to this bronchoconstrictor agent in subjects with allergic rhinitis. <i>Objective:</i> The aim of this study was to determine the effect of inhaled acetaldehyde on lung function in nonasthmatic subjects with allergic rhinitis. <i>Methods:</i> A total of 78 adults (43 subjects with allergic rhinitis, 16 asthmatics and 19 healthy subjects) were challenged with increased concentrations of acetaldehyde and methacholine. The response to each bronchoconstrictor agent was measured by the provocative concentration required to produce a 20% fall in FEV<sub>1</sub> (PC<sub>20</sub>). <i>Results:</i> The geometric mean PC<sub>20</sub> acetaldehyde value for asthmatics was 35.5 mg/ml compared with 67.6 mg/ml in subjects with allergic rhinitis and with 80.0 mg/ml in healthy subjects (p < 0.001). The PC<sub>20</sub> acetaldehyde values in the allergic rhinitis group were also significantly lower than in the healthy control group (p = 0.04). All of the subjects with allergic rhinitis and increased responsiveness to acetaldehyde showed airway hyperresponsiveness to methacholine, but 9 patients with hyperresponsiveness to methacholine failed to respond to acetaldehyde. <i>Conclusions:</i> We conclude that subjects with allergic rhinitis are less responsive to inhaled acetaldehyde than asthmatic subjects, but more than healthy controls. Furthermore, only approximately half the patients with allergic rhinitis and airway hyperresponsiveness to methacholine exhibit bronchoconstriction with inhaled acetaldehyde, thus suggesting that airway hyperresponsiveness to methacholine may not be the sole factor leading to bronchoconstriction in response to acetaldehyde.