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

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.

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.

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 FEV(1) more than 45% of the predicted value. The obstruction-dominant subtype had an emphysema index < or = 20% and FEV(1) < or = 45%, the mild-mixed subtype had an emphysema index < or = 20% and FEV(1) > 45%, and the severe-mixed subtype had an emphysema index > 20% and FEV(1) < or = 45%. Patients were recruited prospectively and treated with 3 months of combined inhalation of long-acting beta-agonist and corticosteroid.

After 3 months of combined inhalation of long-acting beta-agonist and corticosteroid, obstruction-dominant subtype patients showed a greater FEV(1) increase and more marked dyspnea improvement than did the emphysema-dominant subgroup. The mixed-subtype patients (both subgroups) also showed significant improvement in FEV(1) compared with the emphysema-dominant subgroup. Emphysema-dominant subtype patients showed no improvement in FEV(1) or dyspnea after the 3-month treatment period.

The responses to 3 months of combined inhalation of long-acting beta-agonist and corticosteroid differed according to COPD subtype.