Quality assurance of data collection and data processing in epidemiologic studies

Quality assurance of the data generating processes in epidemiologic studies is a prerequisite for the internal validity of study results. This paper p resents practical aspects of such a quality assurance system pertaining to the planning, data gathering, data entry and data processing phase of a stu dy. It is concerned with data obtained in the framework of a project rather than with data accumulating continuously in private practices, research in stitutes or veterinary faculties. During the planning phase of a project, s tandard operating protocols should be developed that assure a reliable perf ormance of observation, coding and data entry. The data base structure, con sisting of tables, input validation rules and queries, should be predefined and well documented. A data safety concept will provide the necessary inte grity, physical safety and availability of the data. The paper presents tec hnical solutions to common data processing problems with emphasis on re-cod ing and relational data base facilities (Microsoft-ACCESS) using a hypothet ical study on risk factors for mastitis.