A novel approach to data collection in a case-control study of cancer and occupational exposures

Background. In community and hospital-based case-control studies, the occupational data collected in interviews are usually limited to responses to general questions asked of all study subjects. A procedure is described in which more detailed information can be collected in an efficient, standardized and systematic way. Methods. A generic work history is initially collected from all subjects using a computer-assisted interview. The work history includes job title, type of business, job activities, materials and chemicals, and tools and equipment used. After responses are entered into the computer by the interviewer, the computer searches a synonym file to identify possible job-specific modules relevant to the reported job. The modules are detailed questionnaires that address specific jobs administered after obtaining the generic work history. The modules are used to ask questions about the work environment; sources of exposure; factors affecting the movement of the agent from the source to the subject, such as local exhaust ventilation; and individual and job characteristics. After the interview is completed, the work history and responses to the modules are sent electronically to an industrial hygienist who reviews the information using a custom-designed software package. Where ambiguities or contradictions occur in information reported by the respondent, or for jobs for which no module had been developed, the industrial hygienist generates up to 10 additional questions per job. These questions are sent back to the interviewer for administration of a short, second interview. Conclusions. These procedures, which are being successfully implemented in an on-going case-control study of brain tumours, should improve disease risk estimates over those derived from more traditional approaches to exposure assessment.