Patients in Wales are often registered on multiple clinical systems depending on how and where they receive care. It is very difficult to link the data from the various systems together and hence to collate the clinical information together to present to care providers. To overcome these issues, NHS Wales has an Electronic MPI (Master Patient Index) which helps maintain and link identities of patients across various clinical systems within Wales. The MPI system was originally procured from Initiate Systems (now taken over by IBM) several years back. The system is linked up to a large number of systems like PASs (Patient Administration Systems), Welsh Demographic Service (WDS), Radiology systems, LIMS (Laboratory Information Management Systems), WCP (Welsh Clinical Portal) amongst others.

These systems use the MPI for providing and receiving latest patient demographics data and for querying the MPI for patient demographics as required but all systems do not use all the services provided by the MPI. The MPI is an intelligent system, which uses algorithms to match patient records based on configured criteria.

All interactions with the MPI system use the HL72.5 messaging standard and are either TCP pipe and hat based or web services based depending on the type of interaction. All notification messages are channelled routed using the Integration service in DHCW.