Measuring symptom occurrence and symptom distress: Development of the symptom experience index

Aim. This paper is a report of a study to assess reliability and construct validity of revised and refined version of the Adapted Symptom Distress Scale: the Symptom Experience Index (SEI). Background. The development of the SEI, a 41-item Likert Scale assessing 20 symptoms, was based on self-regulation theory and an integrative conceptual analysis of symptom assessment and management. The model emphasizes the difference between the occurrence of a symptom (or multiple symptoms) and the distress (emotional) response to the occurrence of a symptom. It is the distress from symptom occurrence that promotes a person to take action and use known coping strategies to prevent the symptom occurrence or alleviate the distress from the symptom. Method. A contrast-group and test-retest approach was used to assess construct validity and reliability with a convenience sample of 158 patients at United States of America in 2003-2004. Results. The SEI demonstrated reasonable internal consistency with a Cronbach's alpha of 0.91 for symptom experience, 0.85 for symptom occurrence and 0.84 for symptom distress. Test-retest reliability was supported by high intra-class correlation coefficients (symptom experience r = 0.93; symptom occurrence r = 0.94; symptom distress, r = 0.92). Construct validity was supported by statistically significant differences between patients and healthy adults. Conclusion. The SEI can be used as a baseline and outcome measure to assess the impact of multiple symptoms on patients, and the effectiveness of interventions to manage these symptoms.