An assessment of the validity of questionnaire responses provided by a surviving spouse

Studies of the etiology of rapidly fatal diseases often use data from surrogate sources. To assess the validity of the wife as a source of exposure information, 80 wives were interviewed in 1983-1984 for the same histories provided earlier by their husbands, who were cases in a case-control study of lung cancer in New Mexico, 1980-1982. Both interviews obtained detailed information concerning lifetime occupational history, smoking habits, and consumption of certain foods high in vitamin A. With regard to lifetime occupational histories, the wives reported significantly fewer jobs. Concordance of the coded histories was approximately 50% for occupation and industry, but was higher for the last job and usual job held. Wives correctly reported the cigarette smoking status of their husbands. For the number of cigarettes smoked per day, wives tended to report 20 cigarettes smoked even when their husbands smoked substantially more or less. The mean frequencies of consumption of certain food items based on the two sources were comparable. However, the percentage of exact agreement and the kappa statistics were generally low.