The march from subclinical small-airways dysfunction to asthma in children with allergic rhinitis

Abstract

Background: Subtle changes in respiratory mechanics may precede the development of asthma in children with allergic rhinitis (AR). Here, we assessed the progression from subclinical small-airways dysfunction to asthma in such patients. Methods: 73 children (age 6 years) with intermittent AR were monitored for asthma development over a period of 5 years. Participants underwent measurements of respiratory resistance (Rrs) and reactance (Xrs) (forced oscillations technique) twice per year: a) when asymptomatic and, b) upon AR exacerbation. The reversibility (Δ) of Rrs and Xrs (400 μg salbutamol) was assessed annually prior to the event (i.e., asthma symptoms) in those who developed asthma or until the end of the follow-up in controls. Results: 23 children (31.5%) developed asthma after a period of 3.5 ±1.1 years. In the absence of nasal symptoms, there were no major prior-to-event changes in ΔRrs and ΔXrs (Figure 1A). At AR exacerbation, however, those who subsequently developed asthma had higher ΔRrs and ΔXrs at least 2 and 4 years, respectively, prior to the event (Figure 1B). In particular, the predictive ability of ΔXrs one year prior to asthma symptoms was excellent (AUC 0.936). Conclusion: In children with AR, subtle changes in respiratory mechanics at the exacerbation of nasal symptoms (i.e., during “natural provocation”) may be predictive of asthma development long before the emergence of asthma symptoms.