Background: As part of the development in information technology, increasing amounts of health care data are available for epidemiological research.
Methods: In this review, we discuss the following factors affecting the value of secondary data in research: 1) completeness of registration of individuals, 2) the accuracy and degree of completeness of the registered data, 3) the size of the data source, 4) the registration period, 5) data accessibility, availability and cost, 6) data format, and 7) possibilities of linkage with other data sources (record linkage).
Results and conclusion: The importance of these issues depends on the use of the data and on the problems they have to address. If the evaluation is satisfactory with respect to the above-mentioned factors relevant to the particular study, the data source could be a very cost-effective way of solving the research problem.