Responses to inhaled long-acting beta-agonist and corticosteroid according to COPD subtype

Rationale: Chronic obstructive pulmonary disease (COPD) is a complex and heterogeneous disorder in which a number of different pathological processes lead to recognition of patient subgroups that may have individual characteristics and distinct responses to treatment. Objectives: We tested the hypothesis that responses of lung function to 3 months of combined inhalation of long-acting beta-agonist and corticosteroid might differ among patients with various COPD subtypes. Methods: We classified 165 COPD patients into four subtypes according to the severity of emphysema and airflow obstruction: emphysema-dominant, obstruction-dominant, mild-mixed, and severe-mixed. The emphysema-dominant subtype was defined by an emphysema index on computed tomography of more than 20% and FEV₁ more than 45% of the predicted value. The obstruction-dominant subtype had an emphysema index ≤ 20% and FEV₁ ≤ 45%, the mild-mixed subtype had an emphysema index ≤ 20% and FEV₁ > 45%, and the severe-mixed subtype had an emphysema index > 20% and FEV₁ ≤ 45%. Patients were recruited prospectively and treated with 3 months of combined inhalation of long-acting beta-agonist and corticosteroid. Results: After 3 months of combined inhalation of long-acting beta-agonist and corticosteroid, obstruction-dominant subtype patients showed a greater FEV₁ increase and more marked dyspnea improvement than did the emphysema-dominant subgroup. The mixed-subtype patients (both subgroups) also showed significant improvement in FEV₁ compared with the emphysema-dominant subgroup. Emphysema-dominant subtype patients showed no improvement in FEV₁ or dyspnea after the 3-month treatment period. Conclusion: The responses to 3 months of combined inhalation of long-acting beta-agonist and corticosteroid differed according to COPD subtype.