Proxy reliability: Health-related quality of life (HRQoL) measures for people with disability

Objectives: Research and surveillance activities sometimes require that pro xy respondents provide key exposure or outcome information, especially for studies of people with disability (PWD). In this study, we compared the hea lth-related quality of life (HRQoL) responses of index PWD to proxies. Meth ods: Subjects were selected from nursing home, other assisted living reside nces, and from several clinic samples of PWD. Each index identified one or more proxy respondents. Computer-assisted interviews used a random order of measures. Proxy reliability was measured by intraclass correlation (ICC) a nd kappa statistics. HRQoL measures tested included the surveillance questi ons of the Behavioral Risk Factor Surveillance System (BRFSS), basic and in strumental activities of daily living (ADLs and IADLs), medical outcomes st udy short-form 36 and 12 (SF-36 and SF-12). Results: A total of 131 index-p roxy sets were completed. In general, agreement and reliability of proxy re sponses to the PWD tended to be best for relatives, with friends lower, and health care proxies lowest. For example, the ICC for the physical function ing scale of the SF-36 was 0.68 for relatives, 0.51 for friends, and 0.40 f or healthcare proxies. There was a tendency for proxies to overestimate imp airment and underestimate HRQoL. This pattern was reversed for measures of pain, which proxies consistently underestimated. The pattern among instrume nts, proxy types, and HRQoL domains was complex, and individual measures va ry from these general results. Conclusions: We suggest caution when using p roxy respondents for HRQoL, especially those measuring more subjective doma ins.