The use of interviews with surrogate respondents in a case-control study of oral cancer.

The purpose of this study was to assess the possible bias that may occur in case-control studies when exposure information is not collected from all potentially eligible cases. The data used in this study were collected in the metropolitan area of Atlanta as part of a multicenter, population-based, case-control study of oropharyngeal cancer. In-person interviews were conducted with 112 cases (67.9 percent) and information on an additional 23 ill or deceased cases (13.9 percent) was collected through surrogate respondents. The cases about whom information was collected from surrogate respondents had more advanced disease at the time of diagnosis and were more likely to be black and less educated than cases who were interviewed in person. Cigarette smoking and consumption of hard liquor were more common among the cases about whom information was collected through surrogates. Therefore, failure to include such information would have resulted in underestimates of the strength of association between these exposures and the risk of oropharyngeal cancer.