Figure 2).

Model A represents the economic model describing combination therapy (CT) versus long-acting beta₂-agonist (LABA) monotherapy based on three trials using a forced expiratory volume in 1 s (FEV₁) of less than 50% predicted as the cut-off for stage 2 chronic obstructive pulmonary disease (COPD) (17,19,20). Model B uses the identical economic model but clinical outcomes from the Towards a Revolution in COPD Health (TORCH) trial (18) are included with the previous three studies. The FEV₁ cut-off for stage 2 COPD was less than 60% predicted and therefore patients with milder COPD are included in this analysis. Note that that model is weighted according to patient numbers in each study and therefore model B is heavily weighted toward clinical outcomes of TORCH. QALY Quality-adjusted life year