Practical guidelines for assessing the clinical significance of health-related quality of life changes within clinical trials

Health-related quality of life (HRQOL) assessment is becoming common practice in many clinical trials. There is much debate over how to determine the clinical significance of changes in HRQOL scores. A number of techniques have been used to address this issue. This paper reviews the most popular of these approaches for use in a clinical trial setting. More specifically, the anchor-based "minimal clinically important difference" technique is described and critiqued, as is the more traditional distribution-based effect size technique. A novel application of effect size, which applies a common statistical premise known as the empirical rule, is also presented. The review of these techniques indicates that there is no single, optimal solution to determining clinical significance of changes in HRQOL scores. However, it is encouraging to note that they all suggest a similar criterion of a half standard deviation for whether or not a change in HRQOL score is clinically significant. Recommendations are given for reporting the clinical significance of HRQOL assessments in clinical trials.