The French Multiple Sclerosis Registry (OFSEP) is a tool aimed at answering many questions about MS. Although it already provides crucial information, some data is still necessary to get a full picture.

The linkage between OFSEP data and the French National Health Data System (SNDS), especially the data from French Health Insurance allows to enrich OFSEP data. The whole set of linked data represents a data warehouse (Entrepôt de données de santé - EDS).

SNDS covers 98% of the French population. Therefore, it contains unprecise healthcare-related data, and even less information about MS.

The OFSEP-SNDS linkage, within the framework of the data warehouse (EDS), combines both of these databases’ advantages.

This data warehouse goals are:

• Analysing recruitment bias in the OFSEP in order to know if the results of the data analysis are representative of all the French MS patients;
• Analysing MS-induced economic costs among OFSEP population and French MS population;
• Enriching OFSEP data thanks to SNDS data (e.g.: drugs taken for another disease) in order to make some new studies possible.