Security aspects of medical file regrouping for the epidemiological follow-up

To carry out epidemiological studies at a regional level, one may need to link information collected by medical doctors working either in hospitals or in private offices or laboratories. The first problem is to respect the European legislation on nominal data processing, which does not allow the linkage of nominal files. As a consequence, we have developed an anonymous record linkage procedure, which ensures an irreversible transformation of identity and allows the linkage of rendered anonymous files. The second problem is to ensure data security during the transmission and we discuss the advantages of different methods of communication such as the norms X400 and Internet protocols.