Analysis and interpretation of health-related quality-of-life data from clinical trials: basic approach of The National Cancer Institute of Canada Clinical Trials Group.

Clinicians are being confronted with increasing amounts of health-related quality of life (HRQOL) data. Thus, there is a need for a greater understanding of the analysis and interpretation of HRQOL so that the data can be reported in an appropriate manner. The approach of the Clinical Trials Group of the National Cancer Institute of Canada emphasises the clinical meaning of the results, while avoiding complex statistical modelling. It consists of four steps: calculating the questionnaire completion rates, calculating the baseline scores, determining the individual change in scores over time for the domains specified in the trial hypothesis, and culminates in determining the proportions of patients who have reported clinically meaningful changes in scores since baseline. A rationale supporting each step is given. This approach is presented as a simple and practical aid to the analysis, interpretation and reporting of HRQOL results.