Outcomes and markers in the assessment of chronic obstructive pulmonary disease

The clinical presentation of chronic obstructive pulmonary disease (COPD) is highly variable, reflecting the interaction of a complex range of pathological changes including both pulmonary and systemic effects. The consequences of COPD experienced by the patient (i.e. its outcomes) include: symptoms, weight loss, exercise intolerance, exacerbations, health-related quality of life, health resource use and death. No single measure can reflect the variety of pathological effects or adequately describe the nature or severity of COPD. Currently, there are few validated markers for assessing COPD and evaluating the effectiveness of treatment. The forced expiratory volume in one second has been used as a global marker of COPD, but it does not fully reflect the burden of COPD on patients. New markers are needed to better characterise the full clinical spectrum of the disease and to guide the development and assessment of new and more effective therapies. This article considers the distinction between outcomes and markers, the various ways in which markers are used and the need for new markers in the management of chronic obstructive pulmonary disease. The process of marker selection and validation is reviewed and potential new biological, physiological and symptomatic markers for chronic obstructive pulmonary disease are assessed.