A review of the reliability and validity of the Edmonton Symptom Assessment System

BACKGROUND Systematic symptom reporting by patients and the use of questionnaires such as the Edmonton Symptom Assessment System (ESAS) have potential to improve clinical encounters and patient satisfaction. We review findings from published studies of the ESAS to guide use of the system and to focus research. METHODS A systematic search for articles from 1991 through 2007 found thirty-nine peer-reviewed papers from 25 different institutions, thirty-three of which focused on patients with cancer. Observations, data, and statistics were collated according to relevance, reliability, validity, and responsiveness. RESULTS Findings apply predominantly to symptomatic palliative patients with advanced cancer who were no longer receiving active oncologic therapies. Uncertainty about summarizing findings arises from frequent modification of the ESAS (altered items, scales, and time periods). Overall, reliability is established for daily administration. Scores are skewed, with a floor effect, but the relative order of symptoms by mean scores is similar across studies. Emotional symptoms are poorly captured by the depression and anxiety items. An equally weighted summation of scores may estimate a construct of "physical symptom distress," which in turn is related to performance status, palliative goals, quality of life, and well-being. CONCLUSIONS The ESAS is reliable, but it has restricted validity, and its use requires a sound clinical process to help interpret scores and to give them an appropriate level of attention. Research priorities are to further develop the ESAS for assessing a greater number of important physical symptoms (and to target "physical symptom distress"), and to develop a similar instrument for emotional symptoms.