Evaluation of two instruments of perceived symptom intensity in palliative care patients in an outpatient clinic

Aims and objectives: To evaluate the test-retest stability in assessments of perceived symptom intensity on the Edmonton Symptom Assessment System-revised and the European Organization for Research and Treatment of Cancer, Quality of Life Questionnaire Core 15 Palliative. The possible interchangeability between the instruments and the patients' experiences of completing the instruments were also studied.

Background: The two instruments assess the same symptoms, but the symptom intensity is assessed on 11-point numerical scales on the Edmonton Symptom Assessment System-revised and on four-point verbal descriptive scales on the European Organization for Research and Treatment of Cancer, Quality of Life Questionnaire Core 15 Palliative. Both instruments are commonly used; however, uncertainty exists about which instrument should be recommended and about the interchangeability of the instruments.

Design: This study used a test-retest design with inter-scale comparisons.

Methods: Data from 54 patients with cancer who were receiving palliative care in an oncology outpatient clinic were self-reported by the patients in the clinic, at home and when patients returned to the clinic.

Results: The assessments on the European Organization for Research and Treatment of Cancer, Quality of Life Questionnaire Core 15 Palliative verbal rating scales showed a higher level of test-retest stability than the assessments on the Edmonton Symptom Assessment System-revised numerical scoring scales, indicating higher reliability. The correspondence between the verbal categories and the numerical scores of symptom intensity were low because different verbal categories were used by patients who assessed the same numerical score.

Conclusions: The test-retest stability in the assessments was higher on the European Organization for Research and Treatment of Cancer, Quality of Life Questionnaire Core 15 Palliative and the results show that assessments on the two instruments could not be used interchangeably. Therefore, the symptom instrument chosen must be specified and unchanged within a patient to improve efficacy in clinical practice.

Relevance to clinical practice: The Edmonton Symptom Assessment System-revised or the European Organization for Research and Treatment of Cancer, Quality of Life Questionnaire Core 15 Palliative can be used for initial assessments of patients, but should not be compared or used interchangeably. It is vitally important to have individual follow-up for all patients who score an instrument.