Patients with chronic obstructive pulmonary disease (COPD) present with a variety of symptoms and pathological consequences. Although primarily viewed as a respiratory disease, COPD has both pulmonary and extrapulmonary effects, which have an impact on many aspects of physical, emotional, and mental well-being. Traditional assessment of COPD relies heavily on measuring lung function, specifically forced expiratory volume in 1 second (FEV(1)). However, the evidence suggests that FEV(1) is a relatively poor correlate of symptoms such as breathlessness and the impact of COPD on daily life. Furthermore, many consequences of the disease, including anxiety and depression and the ability to perform daily activities, can only be described and reported reliably by the patient. Thus, in order to provide a comprehensive view of the effects of interventions in clinical trials, it is essential that spirometry is accompanied by assessments using patient-reported outcome (PRO) instruments. We provide an overview of patient-reported outcome concepts in COPD, such as breathlessness, physical functioning, and health status, and evaluate the tools used for measuring these concepts. Particular attention is given to the newly developed instruments emerging in response to recent regulatory guidelines for the development and use of PROs in clinical trials. We conclude that although data from the development and validation of these new PRO instruments are emerging, to build the body of evidence that supports the use of a new instrument takes many years. Furthermore, new instruments do not necessarily have better discriminative or evaluative properties than older instruments. The development of new PRO tools, however, is crucial, not only to ensure that key COPD concepts are being reliably measured but also that the relevant treatment effects are being captured in clinical trials. In turn, this will help us to understand better the patient's experience of the disease.
Keywords: chronic obstructive pulmonary disease; dyspnea; exacerbations; health-related quality of life; patient-reported outcomes; questionnaire development.