Goals of work: The Edmonton Symptom Assessment System (ESAS) is a tool for self-reporting of symptom intensity, initially developed for advanced cancer patients. It consists of numerical rating scales for nine common symptoms, with the option of adding a tenth. Despite its widespread use in palliative care, few studies have focused on its psychometric properties, with none involving patient perspectives. The purpose of this study was to gather validity evidence for the ESAS, by examining patients' cognitive processes while completing the ESAS, understanding of terminology and numerical ratings, and opinions of the ESAS as a self-reporting tool.
Materials and methods: English-speaking advanced cancer patients, referred to a Pain and Symptom Control Consultation Service in a cancer centre, were recruited. Using a qualitative "think aloud" study design, patients completed the ESAS independently while being prompted to verbalize their thoughts. They then answered a structured questionnaire to elicit their opinions of the ESAS. Transcripts of audio-taped sessions were coded and analyzed.
Main results: Twenty patients were evaluable. Symptom ratings were influenced by current symptom profiles, temporal changes, symptom experience history and individual perceptions. Symptom interpretation and numerical rating assignments varied. Difficult terminology included tiredness versus drowsiness, depression, anxiety, appetite, and well-being. Most patients agreed with the item order and thought that the ESAS was easy to complete, with a health care professional present. Patients expressed a need to emphasize the timeframe as "now".
Conclusion: Modification of the tool and administration process may be warranted, but further study in other populations is needed.