Changes in indices of airway hyperresponsiveness during one year of treatment with inhaled corticosteroids in patients with asthma

We analysed the changes in indices of airway hyperresponsiveness, including hypersensitivity and hyperreactivity, during one year of treatment with in haled corticosteroids We then investigated on which of them the inhaled cor ticosteroids had a primary effect. Fifty outpatients with asthma were recru ited and treated with inhaled beclomethasone dipropionate. They underwent b ronchoprovocation tests on the initial visit and at 3, 6, and 12 months. Th e dose of methacholine required to produce a 20% fall in the forced expirat ory volume in 1 second (PD20-FEV1) was measured to evacuate airway hypersen sitivity. A relatively novel index, the percent change in the forced vital capacity (Delta FVC%) at the PD20-FEV1, was assessed as a marker of airway hyerreactivity. PD20-FEV1 and Delta FVC% were assumed to indicate the horiz ontal shift of the dose-response curve and the vertical change in the maxim al response plateau, respectively: Log(PD20-FEV1) and Delta FVC% continued to improve throughout the year (p < 0.001 and p = 0.002, respectively). Log (PD20-FEV1) improved significantly at the 3-month evaluation (p < 0.001). a nd Delta FVC% improved at the 6-month evaluation (p = 0.012). Log(PD20-FEV1 ) had no or weak relationships with Delta FVC% at all evaluation points. In conclusion, inhaled corticosteroids continued not only to reverse the left ward shift of the cun'e, bur also to restore the plateau.