Cost effectiveness of pharmacological maintenance treatment for chronic obstructive pulmonary disease: a review of the evidence and methodological issues.

Over 200 million people have chronic obstructive pulmonary disease (COPD) worldwide. The number of disease-year equivalents and deaths attributable to COPD are high. Guidelines for the pharmacological treatment of the disease recommend an individualized step-up approach in which treatment is intensified when results are unsatisfactory.