Quality checks, in SIDIAP database, to identify duplicate patient identification are performed centrally at the time of each SIDIAP database update. Furthermore, checks for logic values are performed and unexpected values are dismissed. A part from that, a number of papers have been published on the validity of SIDIAP coding for various conditions. The quality and consistency of the central Catalan register is very good with a built-in validation to detect problems and inconsistencies between variables. In addition, the system is periodically externally validated to ensure quality of data, as these data are used to control payment to service providers.