Background: In a previous study, we developed a 24-item Terminal Delirium-related Distress Scale (TDDS) specifically to evaluate patient and family distress due to terminal delirium. To reduce the burden on terminally ill patients and their families, a scale with fewer evaluation items would be desirable. This study developed the Terminal Delirium-related Distress Scale Short-Form and examined its validity and reliability.
Methods: We tried to remove items not to have sufficient loadings (<0.6) from the TDDS by factor analysis. And palliative care experts reviewed each item and checked the structure of the scale. After that, we developed the TDDS-SF, a 15-item questionnaire consisting of four subscales (care for the family, ability to communicate, psychiatric symptoms and adequate information and discussion about treatment for delirium). We then examined its validity and reliability. The study participants were adult bereaved families of adult patients with cancer who died at participating hospices/palliative care units. The validity of this scale was investigated by evaluating its construct validity, convergent validity, discriminant validity, and internal consistency. As for reliability, we calculated the Cronbach’s alpha coefficient to identify internal consistency.
Results: The study participants were 366 bereaved family members. Factor analysis showed that the construct validity was good. Convergent validity was demonstrated using correlation with the Care Evaluation Scale (r= -0.54, P< 0.001) and the Good Death Inventory (r= -0.54, P< 0.001). Discriminant validity was demonstrated by a low correlation (r= 0.23, P< 0.001) with the distress score felt by the bereaved family. Internal consistency was also good (Cronbach's alpha = 0.70-0.94).
Conclusion: The TDDS-SF is a valid and feasible measure for irreversible terminal delirium-related distress.