How to ensure data security of an epidemiological follow-up: quality assessment of an anonymous record linkage procedure.

A computerised record hash coding and linkage procedure is proposed to allow the chaining of medical information within the framework of epidemiological follow-up. Before their extraction, files are rendered anonymous using a one-way hash coding based on the standard hash algorithm (SHA) function, in order to respect the legislation on data privacy and security. To avoid dictionary attacks. two keys have been added to SHA coding. Once rendered anonymous, the linkage of patient information can be accomplished by means of a statistical model, taking into account several identification variables. Quality assessment of this anonymous record linkage procedure shows a specificity of 100% and a sensitivity of 95%.