Measuring health status in chronic airflow limitation.
A health status instrument for use in clinical trials must be valid (measuring what it is supposed to measure) and responsive (able to detect clinically important change). Approaches to measuring health status in clinical trials include using a battery of instruments, a general instrument which provides a profile of the patient's health, an instrument that generates a health utility, or an instrument that focuses on the problems associated with a particular disease. Disease-specific instruments have been used in clinical trials in chronic airflow limitation (CAL). The Oxygen Cost Diagram is simple and easy to administer, but responsiveness and validity are unproven. The Transition Dyspnoea Index is valid and responsive, but is difficult to use in trials in which multiple measurements are desired. The Chronic Respiratory Disease Questionnaire has proved valid and responsive in controlled trials in CAL patients. Health status measures should be included in all clinical trials in CAL.