Minimal clinically significant difference in health status: the thorny path of health status measures?

Abstract

Health status or health-related quality of life is being recognized as an important outcome when evaluating patients with chronic pulmonary disease. There is growing literature about health status measures in patients with asthma and chronic obstructive pulmonary disease (COPD). The European Respiratory Journal (ERJ) has published numerous articles on issues related to health status. The authors believe that the ERJ is a valuable resource in this area, especially for summarizing updated issues on the health status of pulmonary disease 1, or validating new questionnaires or comparing health status measures. Clinicians need to understand and critically evaluate measurements of health status in order to determine if a new therapy could be applied to their own patients with expectation of improving their health status. However, it is also true that many readers face confusion and difficulty in interpreting the results of health status measures. Important concepts when evaluating measurements of health status are the clinically significant threshold or the minimal clinically significant difference (MCSD) 2. When health status is measured using a continuous scale, it needs to be known whether an observed difference indicates a clinically significant or trivial effect on the patients' health status or quality of life. A statistically significant difference in health status might be of little practical importance; it is more important to know the MCSD. There are several definitions of the MCSD that correspond to the perspective of those who evaluate. For example, Jaeschke et al. 3 define “minimal clinically important difference” as the smallest difference in a score in a domain of interest that patients perceive as beneficial and that would mandate, in the absence of side-effects and a change in the patient's management 3. In the …