Grand Duchy of Luxembourg: a case study of a national master patient index in production since five years.

Background: Unequivocal identification of patients is a precondition for a safe medical journey through different information systems (ISs) and software applications that are communicating and exchanging interoperable data. A master patient index (MPI) can facilitate this task. Being a repository of patient identity traits, a MPI allows an accurate surveillance of the patients' "medical identities".