Proxy respondents and the validity of occupational and other exposure data. The Selected Cancers Cooperative Study Group.

As part of a multicenter cancer case-control study conducted in 1984-1988, a proxy interview was attempted for all cases who were initially interviewed for the study but who died during the 4-year data collection period. To assess the validity of using wives, other relatives, or other informants to obtain information about a subject, the authors compared occupational and other exposure data obtained from 270 male cancer cases and their proxy respondents. The primary focus of the case-control study was on Vietnam military service and exposure to phenoxy herbicides, but cases and their proxy respondents were also asked about occupational and other exposures relevant to the cancers. The accuracy of reporting for specific occupational exposures (e.g., asbestos and formaldehyde) and specific occupations (e.g., dry cleaning and meat packing or processing) was poor, although the latter improved somewhat when only case-spouse pairs were examined. Similarly, there was poor sensitivity in the reporting of herbicide exposure information in farming and other related occupations. In contrast, the reporting of certain demographic characteristics, childhood history characteristics, and use of alcohol and cigarettes was relatively good, and was even better when only case-spouse pairs were examined. The poor quality of proxy information for detailed exposure information suggests the need for careful use and interpretation of proxy information in epidemiologic studies.