How do proxy responses and proxy-assisted responses differ from what Medicare beneficiaries might have reported about their health care?

Health Services Research, June, 2008 by Marc N. Elliott, Megan K. Beckett, Kelly Chong, Katrin Hambarsoomians, Ron D. Hays

Surveys of the recipients of health care are increasingly important means of assessing the care provided by health plans, hospitals, physicians, and other entities (Lied et al. 2003; Tai-Seale 2004; Darby, Hays, and Kletke 2005). At the same time, an aging population means that more patients are unable to answer surveys themselves. The use of proxy respondents provides a practical solution to survey nonresponse and missing data attributable to limitations in the ability of patients, beneficiaries, or nursing home residents to respond themselves. By asking representatives to respond on behalf of the patient, survey researchers need not omit the experiences of the least healthy and most vulnerable. For these reasons, most health care surveys allow the use of proxy respondents. Yet, questions inevitably arise about whether proxies give responses comparable to what might have been self-reported. One might ask whether there is systematic bias or substantial decrement in reliability from the use of proxy responses that erodes much of the apparent gains from reducing the selective omission of those needing assistance in responding.

Prior research on proxy response has largely focused on differences between self- and proxy responses reporting on the experiences of the same individual. Much of this work has taken place with small convenience samples of patients, often with severe health problems (e.g., end-of-life, schizophrenia, or lung cancer) (Kutner et al. 2006; Hoe et al. 2007; Wennman-Larsen et al. 2007). In such a design, any differences between the self- and proxy responses are because the proxy is reporting on the same experiences in a different way than self-respondents. While typically in poor health, targets in these studies are by definition able and willing to provide self-responses, and thus differ fundamentally from individuals who require proxy assistance. Those who are unable to respond for themselves are not represented in these prior studies and may differ in other important ways.

This prior research finds that proxies can both over- and underestimate morbidity and disability (Magaziner et al. 1988; Sneeuw et al. 1997; Shaw, McColl, and Bond 2000; Todorov and Kirchner 2000; Duncan et al. 2002; Tang and McCorkle 2002; Pickard et al. 2004) and other aspects of health-related quality of life (Hays et al. 1995; Andresen, Vahle, and Lollar 2001; Becchi et al. 2004; Higashi et al. 2005; Kutner et al. 2006; Hoe et al. 2007). Proxy reporting differences may be attributable to different cognitive and perceptual strategies to answering questions (Todorov and Kirchner 2000; Stineman et al. 2004; Lynn Snow et al. 2005). Proxy respondents rely on observable factors, such as counts or the presence or absence of a symptom (Lynn Snow et al. 2005), suggesting smaller discrepancies between self- and proxy-reports for objective or observable measures than for subjective measures (Whiteman and Green 1997; Todorov and Kirchner 2000; Sneeuw, Sprangers, and Aaronson 2002; Pickard et al. 2004; Stineman et al. 2004).

The relationship of the proxy to the intended respondent may also influence the accuracy of proxy responses. Some research suggests that spouses and proxies who live with the intended respondent provide responses that are closer to those of the intended respondent than do other family members (Shaw et al. 2000; The Medical Research Council Cognitive Function and Ageing Study 2000). This finding may be a function of both the opportunity for direct observation and of a similarity in perspective attributable to similarity in age, education, and other factors (Qian and Preston 1993) that are known to influence evaluations of health care (Elliott et al. 2001; Zaslavsky et al. 2001).

In nursing homes and other institutional settings, spouses and family members are often less readily available than nonrelative adults, such as health care workers. Several studies examined the similarity of these proxy responses to those from spouses and other relatives (Rubenstein et al. 1984; Becchi et al. 2004; Kane et al. 2005; Kutner et al. 2006). The answer may depend on the subjectivity of the measure. For example, compared with relatives, nurse proxy reports on number of instrumental activities of daily living are closer to patient self-reports (Rubenstein et al. 1984), but nonrelative and relative proxies reports on nursing home resident quality of life were about equally close to resident self-reports.

When beneficiaries are unable to provide responses independently to the CAHPS[R] Medicare Fee-for-Service (MFFS) and Medicare Managed Care (MMC, now Medicare Advantage or MA) surveys, proxies are permitted to participate in ways that range from assistance (by reading the questions, writing down the answers the beneficiary gives, translating the questions into the beneficiary's language, or helping in some other similar manner) to serving as a proxy respondent (i.e., answering about the beneficiary's experiences in place of the beneficiary).