title: External review and validation of the Swedish national inpatient register.
abstract: BACKGROUND
  The Swedish National Inpatient Register (IPR), also called the Hospital Discharge Register, is a principal source of data for numerous research projects. The IPR is part of the National Patient Register. The Swedish IPR was launched in 1964 (psychiatric diagnoses from 1973) but complete coverage did not begin until 1987. Currently, more than 99% of all somatic (including surgery) and psychiatric hospital discharges are registered in the IPR. A previous validation of the IPR by the National Board of Health and Welfare showed that 85-95% of all diagnoses in the IPR are valid. The current paper describes the history, structure, coverage and quality of the Swedish IPR.
  
  
  RESULTS
  In January 2010, we searched the medical databases, Medline and HighWire, using the search algorithm "validat* (inpatient or hospital discharge) Sweden". We also contacted 218 members of the Swedish Society of Epidemiology and an additional 201 medical researchers to identify papers that had validated the IPR. In total, 132 papers were reviewed. The positive predictive value (PPV) was found to differ between diagnoses in the IPR, but is generally 85-95%.
  
  
  CONCLUSIONS
  In conclusion, the validity of the Swedish IPR is high for many but not all diagnoses. The long follow-up makes the register particularly suitable for large-scale population-based research, but for certain research areas the use of other health registers, such as the Swedish Cancer Register, may be more suitable.
authors.affiliation: Department of Paediatrics, Örebro University Hospital, Sweden. jonasludvigsson@yahoo.com
authors.forename: Jonas F
authors.initials: JF
authors.lastname: Ludvigsson
authors.forename: Eva
authors.initials: E
authors.lastname: Andersson
authors.forename: Anders
authors.initials: A
authors.lastname: Ekbom
authors.forename: Maria
authors.initials: M
authors.lastname: Feychting
authors.forename: Jeong-Lim
authors.initials: JL
authors.lastname: Kim
authors.forename: Christina
authors.initials: C
authors.lastname: Reuterwall
authors.forename: Mona
authors.initials: M
authors.lastname: Heurgren
authors.forename: Petra Otterblad
authors.initials: PO
authors.lastname: Olausson
mesh_terms: D000328:Adult; D000368:Aged; D004194:Disease / Q000145:classification; D004813:Epidemiology; D005260:Female; D006801:Humans; D007297:Inpatients / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009017:Morbidity; D012042:Registries / Q000592:standards*; D013548:Sweden / Q000453:epidemiology; D055815:Young Adult