Reliability of information collected by proxy in family studies of Alzheimer's disease

The study evaluated the reliability of data obtained from proxy informants. The index subjects in this study were 81 nondemented participants in the M ulti-institutional Research in Alzheimer Genetic Epidemiology (MIRAGE) stud y. These index subjects and 159 proxy informants, identified by the index s ubjects, participated in the study. The K statistic with multiple raters pe r subject (for dichotomous variables) and the intraclass correlation coeffi cient (for continuous variables) were used to measure reliability. Among pr oxy respondents who provided answers, there was excellent agreement between proxy responses and the responses of the index subjects (0.7 less than or equal to kappa less than or equal to 0.9), with the exception of questions about head injury (kappa = 0.4). A large proportion (> 90%) of the proxy in formants in this study were able to provide information on most items. High er nonresponse rates las high as 30%) were observed for medication history and women's health questions. This study supports the reliability of proxy responses for most categories of questions that are elicited in typical epi demiological studies, including the MIRAGE study. Copyright (C) 2001 S. Kar ger AG, Basel.