Percentage fall in FVC at the provocative concentration of methacholine causing a 20% fall in FEV1 in symptomatic asthma and clinical remission during adolescence

초록

Background: Many children with asthma go into long-term clinical remission at adolescence, hut bronchial hyperresponsiveness (BHR) persists in approximately one half of these subjects. BHR is usually assessed by measuring the provocative concentration of methacholine causing a 20% fall in FEV1 (PC20). The percentage fall in FVC at the PC20 (Delta FVC) has been suggested to be a more useful index of disease severity in asthma than PC20. Study objective: The aim of this study was to determine whether Delta FVC is higher in adolescents with symptomatic asthma than in those with clinical remission. Patients and methods: Forty adolescents with symptomatic asthma and 80 adolescents with asthma remission underwent methacholine challenge testing. Delta FVC and PC20 were measured on the methacholine dose-response curve. Results: The mean (95% confidence interval [Cl]) Delta FVC (15.5% [95% CI, 14.1 to 16.9%]) in the symptomatic group (n = 40) was significantly higher (p = 0.017) than that (12.8% [95% CI, 11.5 to 14.1%]) in the BHR-positive (PC20 < 16 mg/mL) remission group (n = 44) or that (11.5% [95% CI, 10.2 to 12.8%]) of the BHR-negative remission group (n = 36), with no difference between the two latter groups (p = 0.581). No significant correlation was found between Delta FVC and PC20 in the symptomatic group (r = - 0.156, p = 0.336) or in the whole remission group (r = - 0.187, p = 0.097). Conclusions: Adolescents with symptomatic asthma had a higher Delta FVC than those with clinical remission, irrespective of the presence of BHR in the latter group. This finding suggests that Delta FVC may serve as an adjunct marker for differentiating between asthma persistence and remission during adolescence.

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