Measuring agreement between patient and proxy responses to multidimensional health-related quality-of-life measures in clinical trials. An application of psychometric profile analysis.

When patients cannot provide responses to health-related quality-of-life (HRQOL) measures in clinical trials, family or friends may be asked to respond. We present a simple, comprehensive method for assessing agreement between patients with head injury and their proxy responders. In contrast to more traditional approaches, this method defines agreement separately for each patient-proxy pair, and compares HRQOL profiles along three dimensions-level, or the average of the ratings; scatter, or the variability in the ratings; and shape, or the ranks of the ratings. We demonstrate this method in the context of a clinical trial of a treatment for traumatic head injury and compare the results to those obtained using traditional analyses. Options for incorporating proxy responses into clinical trial analyses are discussed.