Proxy evaluation of health-related quality of life: a conceptual framework for understanding multiple proxy perspectives.

Proxy assessment of health-related quality of life (HRQL) may be sought to substitute for, or to complement, patient self-assessment. The viewpoint from which the proxy is asked to assess the patient is a subtle yet important aspect of proxy assessment. Proxy assessments can be elicited by asking a proxy to assess the patient as they think the patient would respond (ie, proxy-patient perspective) or for the proxy to provide their own perspective on the patient's HRQL (ie, proxy-proxy perspective). In this article, we introduce a framework for differentiating between and understanding HRQL assessments according to rater viewpoint. The difference between patient self-assessment and the proxy-patient perspective is defined as the inter-rater gap, whereas the difference between the proxy-patient and proxy-proxy perspective is described as the intra-proxy gap. The inter-rater gap represents the difference between patient self-assessed HRQL and the proxy ability to comprehend the patient view. The extent to which the proxy-proxy perspective is informative will depend upon the proxy's ability to provide reinforcing or complementary information, ie, represented by the intra-proxy gap, on the HRQL of the patient. We refer to the framework to emphasize the importance of delineating between proxy perspectives in study design and HRQL measurement and to guide inquiries into the validity and interpretation of the meaningfulness of the proxy HRQL assessments from each viewpoint. Future research and use of proxy raters of HRQL in clinical trials, population health monitoring, resource allocation, and clinical management can be informed by explicit consideration of the suggested framework.