According to current GOLD strategy, patients with COPD classified as groups A and B may be treated with inhaled bronchodilators, either long-acting β₂-agonist (LABA) or long-acting muscarinic antagonist (LAMA). However, there is little guidance on which class of agent is preferred and a lack of prospective data to differentiate the two.

In this study, we performed post-hoc analyses of pooled data from two prospective, controlled clinical trials comparing the LABA indacaterol and LAMA tiotropium in 1422 patients with moderate airflow limitation and no history of exacerbations in the previous year. This population fits the definitions of GOLD A and B groups and could be further stratified by symptom severity using Baseline Dyspnea Index (i.e. modeling GOLD A or B) and inhaled corticosteroid (ICS) use at baseline. Outcomes measured after 12 weeks of treatment were lung function (forced expiratory volume in 1 s; FEV₁), health status (St George's Respiratory Questionnaire; SGRQ), symptoms (Transition Dyspnea Index; TDI) and rescue medication use.

In ‘GOLD A’ patients not receiving ICS, differences favored indacaterol versus tiotropium (trough FEV₁ 0.05 L; rescue medication use −0.41 puffs/day; TDI total score 0.94 points; SGRQ total score −3.13 units, all p < 0.01). In ‘GOLD B, no ICS’ patients, compared with tiotropium, indacaterol treatment increased trough FEV₁ (0.055 L, p < 0.05) and permitted a larger reduction in rescue medication use (−0.81 puffs/day, p = 0.004). In all patients, and in patients not using ICS, differences favored indacaterol for all variables.

Our findings suggest that patients in GOLD groups A and B may experience greater benefits with indacaterol than with tiotropium.