How valid are family proxy assessments of stroke patients' health-related quality of life?

BACKGROUND AND
PURPOSE: Proxy respondents are often needed to report outcomes in stroke survivors, but they typically systematically rate impairments worse than patients themselves. The magnitude of this difference, the degree of agreement between patients and proxies, and the factors influencing agreement are not well known.
METHODS: We compared patient and family proxy health-related quality of life (HRQL) responses in 225 patient-proxy pairs enrolled in a clinical trial for poststroke depression. We used paired t-tests and the intraclass correlation (ICC) statistic to evaluate the agreement between patient and proxy domain scores and the overall Stroke-specific Quality of Life (SS-QOL) score. We used multivariate linear regression to model patient- and proxy-reported SS-QOL scores.
RESULTS: Patients were older (63 versus 55 years) and less often female (48% versus 74%) than proxies. Proxies rated all domains of SS-SQOL slightly worse than patients. The Mood, Energy, and Thinking domains had the greatest disparity with mean patient-proxy differences of 0.45, 0.37, and 0.37 points, respectively. The ICC for each domain ranged from 0.30 (role function) to 0.59 (physical function). Proxy overall SS-QOL score was also lower (worse) than patient score (3.7 versus 3.4, P<0.001) with ICC of 0.41. Agreement was higher among patient-proxy pairs with higher patient depression scores and with lower proxy report of caregiving burden.
CONCLUSIONS: Proxies systematically report more dysfunction in multiple aspects of HRQL than stroke patients themselves. Agreement between patient and proxy HRQL domain scores is modest at best and is affected by patient depression and proxy perception of burden. These differences may be large enough to impact the outcome assessment in stroke clinical trials.