Measuring symptom distress in palliative care: Psychometric properties of the Symptom Assessment Scale (SAS)
Given the variety of palliative care settings within which symptom distress must be assessed, development of a valid and reliable clinical tool that can be simply applied in every day practice is needed. The Symptom Assessment Scale (SAS) uses a 0-10 numerical scale with zero being no symptom and 10 being the worst possible. The key symptoms included in the scale are breathing, bowel problems, appetite problems, pain, insomnia, nausea and fatigue. The instrument is structured to allow either the patient, family member or nurse to assess the symptoms. The scale was tested on 572 cancer patients recruited from five palliative care services in Western Australia. Results indicated that the instrument was brief, clinically useful and was administered with minimal missing data. Internal consistency reliability estimates of the scale ranged from 0.64-0.92 as measured by the Cronbach's alpha co-efficient. Test-retest reliabilities of 0.84-0.92 were obtained using Pearson's correlation co-efficient. The instrument does not provide an in-depth assessment of individual symptoms, but serves as a screening tool to identify troublesome symptoms that warrant attentive and immediate investigation and comprehensive assessment.