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Conceptual COPD disease progression model. Moderate COPD (forced expiratory volume in 1 s (FEV1) % pred 50 to <80%); severe COPD (FEV1 % pred 30 to <50%); very severe COPD (FEV1 % pred <30%). A recent exacerbation history is defined as an exacerbation occurring within the previous year. QALY: quality-adjusted life year.
