Bronchodilator and corticosteroid reversibility in ambulatory patients with airways obstruction

With the aim of characterising subgroups, we analysed reversibility tests from 1,048 patients with airways obstruction (baseline FEV1 less than 60% of predicted normal (%pred), and FEV1 to FVC ratio less than 0.6). Spirometry before and after inhalation of salbutamol 0.3 mg and ipratropium bromide 0.06 mg was performed before and after one week of treatment with prednisone 30 mg daily. The changes in FEV1 after bronchodilators showed unimodal distribution (mean = 7.0 %pred, st.dev. = 6.6 %pred). The responses to corticosteroid were more spread out (mean = 6.3 %pred, st.dev. = 13.8 %pred). The correlation between bronchodilator responses before and after corticosteroid treatment was poor (r = 0.30), although highly significant (p less than 0.000,001). The responses to bronchodilators were virtually independent of the steroid reversibility. The corticosteroid response was inversely related to age (r = -0.20, p less than 0.000,001) and smoking habits (r = -0.17, p less than 0.000,001), and moderately associated with blood eosinophilia (r = 0.34, p less than 0.000,001). The frequency distribution of the bronchodilator responses and the steroid response and combinations of the responses were all unimodal, making any distinction between nosologic subgroups arbitrary. It is clear from the study that criteria other than just response to therapy must be employed for distinction of subgroups among patients with airways obstruction.