Differences in proxy-reported and patient-reported outcomes: assessing health and functional status among medicare beneficiaries

BACKGROUND: Proxy responses are very common when surveys are conducted among the elderly or disabled population. Outcomes reported by proxy may be systematically different from those obtained from patients directly. The objective of the study is to examine the presence, direction, and magnitude of possible differences between proxy-reported and patient-reported outcomes in health and functional status measures among Medicare beneficiaries. METHODS: This study is a pooled cross-sectional study of a nationally representative sample of community-dwelling Medicare beneficiaries from 2006 to 2011. Survey respondents can respond to the Medicare Current Beneficiary Survey either by themselves or via proxies. Health and functional status was assessed across five domains: physical, affective, cognitive, social, and sensory status. Propensity score matching was used to get matched pairs of patient-reports and proxy-reports. RESULTS: After applying the propensity score matching, the study identified 7,780 person-years of patient-reports paired with 7,780 person-years of proxy-reports. Except for the sensory limitation, differences between proxy-reported and patient-reported outcomes were present in physical, affective, cognitive, and social limitations. Compared to patient-reports, a question regarding survey respondents’ difficulties in managing money was associated with the largest proxy response bias (relative risk, RR = 3.83). With few exceptions, the presence, direction, and magnitude of differences between proxy-reported and patient-reported outcomes did not vary much in the subgroup analysis. CONCLUSIONS: When there is a difference between proxy-reported and patient-reported outcomes, proxies tended to report more health and functional limitations among the elderly and disabled population. The extent of proxy response bias depended on the domain being tested and the nature of the question being asked. Researchers should accept proxy reports for sensory status and objective, observable, or easy questions. For physical, affective, cognitive, or social status and private, unobservable, or complex questions, proxy-reported outcomes should be used with caution when patient-reported outcomes are not available.