Development and Psychometric Validation of the 27 Item Zarit Caregiver Interview for Alzheimer’s Disease (ZCI-AD-27)

BACKGROUND: Caring for an individual with Alzheimer’s disease (AD) is an all-encompassing challenge that affects daily life. Assessment of the care partner experience is needed to support the development and evaluation of successful interventions for people with AD and their care partners. We developed the 27-item Zarit Caregiver Interview for Alzheimer’s Disease (ZCI-AD-27) to assess the impact of informal caregiving in the context of AD. OBJECTIVE: We assessed the psychometric validity of the ZCI-AD-27 in a population of care partners for individuals with moderate AD, and established thresholds for meaningful score change. METHODS: Secondary data were obtained from informal care partners of participants in a clinical trial (NCT01677754). Psychometric analyses were conducted to assess validity, reliability, and responsiveness of the ZCI-AD-27. Anchor-based and distribution-based methods were performed to determine clinically meaningful score change. RESULTS: The ZCI-AD-27 had a 12-domain factor structure, including a second-order domain termed Humanistic impact that included four key domains (Physical, Emotional, Social, and Daily life) as confirmed by confirmatory factor analysis with the adequate fit. Internal consistency (Cronbach’s alpha ranging from 0.66 to 0.93 for domains), convergent validity, and discriminant validity indicated the good performance of the ZCI-AD-27. Known-groups validity analyses showed a greater impact on care partners with increasing disease severity. Responsiveness results demonstrated that the ZCI-AD-27 is sensitive to change over time and meaningful change analyses indicated a range of meaningful score changes in this population. CONCLUSION: The ZCI-AD-27 is a comprehensive, psychometrically valid measure to assess the impact of caring for individuals with moderate AD.