title: The Danish National Patient Register.
abstract: BACKGROUND
  The Danish National Patient Register (NPR) was established in 1977, and it is considered to be the finest of its kind internationally.
  
  
  BACKGROUND
  At the onset the register included information on inpatient in somatic wards. The content of the register has gradually been expanded, and since 2007 the register has included information on all patients in Danish hospitals.
  
  
  RESULTS
  Although the NPR is overall a sound data source, both the content and the definitions of single variables have changed over time. Changes in the organisation and provision of health services may affect both the type and the completeness of registrations.
  
  
  CONCLUSIONS
  The NPR is a unique data source. Researchers using the data should carefully consider potential fallacies in the data before drawing conclusions.
authors.affiliation: Institute of Public Health, University of Copenhagen, Copenhagen, Denmark. elsebeth@pubhealth.ku.dk
authors.forename: Elsebeth
authors.initials: E
authors.lastname: Lynge
authors.forename: Jakob Lynge
authors.initials: JL
authors.lastname: Sandegaard
authors.forename: Matejka
authors.initials: M
authors.lastname: Rebolj
mesh_terms: D003718:Denmark / Q000453:epidemiology; D058006:General Practice / Q000458:organization & administration; D006298:Health Services Administration; D006302:Health Services Research; D006801:Humans; D010346:Patient Care Management; D010361:Patients / Q000145:classification; D011320:Primary Health Care / Q000458:organization & administration; D012042:Registries