The growing number of hemophilia registries: Quantity vs. quality.

Registries for rare diseases provide a tool for obtaining an overview of the clinical situation and can be used to discover points of improvement and to monitor long-term safety. Registries could also become a powerful tool to provide supporting information for marketing authorization. There is an urgent need for a pan-European or global strategy that supports consistent data. Therefore, transparency in data collection, harmonization of the database structures, and the convergence of scientific approaches are required.