Peak expiratory flow variability and exercise responsiveness in methacholine-hyperresponsive adolescents with asthma remission

The aim of this study was to investigate whether bronchial hyperresponsiveness in adolescents with long-term asthma remission is associated with increased peak expiratory flow (PEF) variability and/or increased bronchial response to exercise (BRE). Twenty-nine adolescents with asthma remission (neither symptoms nor any medication used during the previous two years), but with persistent methacholine hyperresponsiveness (PC₂₀ < 18 mg/mL; remission group), 29 methacholine PC₂₀-matched adolescents with symptomatic asthma (symptomatic group), and 20 healthy subjects (control group) were studied. Subjects recorded PEF twice daily for 14 days and PEF variability, expressed as amplitude % mean, was calculated. Subjects also underwent a standardized exercise challenge; BRE was defined as a maximal % fall in FEV₁ within 30 min after exercise. The mean (± SD) PEF variations in the symptomatic group and in the remission group were 12.10 ± 6.35% and 10.02 ± 4.73%, respectively, which were significantly higher than that (5.94 ± 2.44%) of the control group. On the other hand, the degree of BRE (7.36 ± 3.85%) in the remission group was significantly lower than that (22.31 ± 10.50%) of the symptomatic group, and similar to that (5.98 ± 2.70%) of the control group. Methacholine hyperresponsiveness in asthma remission during adolescence is associated with increased PEF variability but not with increased BRE.