Development and validation of the Terminal Delirium-Related Distress Scale - Shortform.

Background: We previously developed a 24-item Terminal Delirium-Related Distress Scale (TDDS) to evaluate patient and family distress due to terminal delirium. However, a scale with fewer evaluation items was needed to reduce the burden on terminally ill patients and their families. Thus, the TDDS Shortform (TDDS-SF) was developed, and the validity and reliability of the scale were evaluated.

Objectives: The aim of this study is to evaluate the validity and reliability of TDDS-SF.

Methods: Items with insufficient loading (<0.6) based on factor analysis were removed from the TDDS. Palliative care experts reviewed each item and checked the structure of the scale. Based on their feedback, we developed the TDDS-SF, a 15-item questionnaire consisting of 4 subscales, including "Care for the family," "Ability to communicate," "Psychiatric symptoms," and "Adequate information and discussion about treatment for delirium." A cross-sectional, self-completed questionnaire survey of bereaved families of cancer patients who were admitted to a hospice/palliative care unit was conducted in August 2018. The survey included the TDDS-SF, Good Death Inventory (GDI), Care Evaluation Scale (CES), and distress score in the Delirium Experience Questionnaire. The validity, including construct validity, convergent validity, discriminant validity, and internal consistency, and reliability, including the Cronbach's alpha coefficient for internal consistency, of the TDDS-SF were evaluated.

Results: The study included 366 bereaved family members. Factor analysis revealed good construct validity. Convergent validity was demonstrated based on good correlations with the CES (r = - 0.54, P < 0.001) and the GDI (r = - 0.54, P < 0.001). Discriminant validity was demonstrated by a low correlation (r = 0.23, P < 0.001) with the distress scores of bereaved families. The internal consistency was also good (Cronbach's alpha = 0.70-0.94).

Significance of results: The TDDS-SF is a valid and feasible tool for assessing irreversible terminal delirium-related distress. A study targeting patients and their families with end-of-life delirium is planned for the near future.