Health status in patients with Alzheimer's disease: An investigation of inter-rater agreement

Objective: The purpose of the present study was to examine the level of agreement between health status ratings provided by patients with Alzheimer's disease and by their proxies. Background: Because proxy-completed responses are often necessary in assessing health outcomes for the elderly, it is necessary to determine the feasibility and potential limitations of using proxies as a patient substitutes. Methods: To assess the potential utility of proxy responses on health status when subjects present a cognitive impairment, this study compared the responses of 70 subjects with Alzheimer's disease and those of their family and/or care provider proxy using the SF-36. Agreement between proxies and patients was measured by intraclass correlation coefficients (ICCs). Results: The proportion of exact agreement between patients and proxies on the 36 items ranged from 3.3 to 41.7%. Results reveal poor to moderate agreement between patient and proxy reports. Proxy reliability varied according to the relationship of the proxy to the index subject. Agreement decreased significantly with increasing severity of dementia and with increasing severity of Physical status (Katz ADL). Agreement was better for measures of functions that are directly observable and relatively poor for more subjective measures. Conclusions: Our results confirm the importance of the information source used for patient health status.