Methodological issues in the assessment of health-related quality of life in palliative care trials.

Palliative care aims at improving the patient's quality of life. Clinical trials, therefore, often include the patient's subjective evaluation of symptoms and psychosocial problems, so-called health-related quality of life (HRQL), as end-points. Unfortunately, there are frequently methodological weaknesses in the assessment of HRQL. This paper discusses four criteria which can be used in the evaluation of the quality of such studies: I. The authors should document that they have included the relevant HRQL issues in the questionnaire. If a trial misses important issues, its results may be misleading. II. The sample size should be sufficient to detect meaningful differences. Many trials are too small. III. The assessment of HRQL should have the appropriate timing, reflecting the research questions. The symptoms and the benefit resulting from treatments are not constant over time and often have cyclic patterns. The results may therefore be dependent on the timing of the administration of questionnaires to patients and on the time frames specified in the instructions. IV. The data must be reasonably complete. Incomplete data cannot be avoided in palliative care research, but missing data due to administrative failures or unrealistic schedules must be avoided. A pilot study may show whether a study is feasible. Missing data are likely to bias results. Many published palliative care studies are suboptimal with regard to one or more of these four criteria. This should be considered when reading published studies and when new trials are planned.