title: Completeness and correctness of cerebral palsy diagnoses in two health registers: implications for estimating prevalence.
abstract: To assess completeness and correctness of cerebral palsy (CP) diagnoses in the Cerebral Palsy Register of Norway (CPRN) and the Norwegian Patient Register (NPR), and to estimate CP prevalence.
  
  
  
  Among 747 883 Norwegian residents born from 1996 to 2007, 2231 had a diagnosis of CP in the NPR while 1441 were registered in the CPRN. Children registered in the CPRN were considered to have a valid CP diagnosis. For those with a diagnosis of CP only in the NPR, two paediatricians reviewed the hospital records. The prevalence rate of CP with 95% confidence intervals (CI) was calculated on the basis of the combined data sets.
  
  
  
  One thousand three hundred and ninety-eight children were registered with a diagnosis of CP in both registers, 43 children were only registered in the CPRN, and 824 only in the NPR. The review of hospital records revealed that 464 (59.5%) had CP. Thus, the NPR was 98% complete, and for 86% the diagnosis was correct. The completeness of the CPRN was 76%, while the diagnosis was considered correct for all children (100%). The resulting prevalence of CP was 2.5 (95% CI 2.4-2.7) per 1000.
  
  
  
  To gain accurate estimates of prevalence rates of CP, it is essential to combine data sources and to validate register data.
authors.affiliation: The Cerebral Palsy Register of Norway, Vestfold Hospital Trust, Tønsberg, Norway.
authors.forename: Sandra Julsen
authors.identifier: 0000-0002-7486-7454
authors.initials: SJ
authors.lastname: Hollung
authors.affiliation: Norwegian University of Science and Technology, Trondheim, Norway.
authors.forename: Torstein
authors.initials: T
authors.lastname: Vik
authors.affiliation: The Norwegian Patient Register, The Norwegian Directorate of Health, Trondheim, Norway.
authors.forename: Robert
authors.initials: R
authors.lastname: Wiik
authors.affiliation: Norwegian Institute of Public Health, Oslo, Norway.
authors.forename: Inger Johanne
authors.initials: IJ
authors.lastname: Bakken
authors.affiliation: The Cerebral Palsy Register of Norway, Vestfold Hospital Trust, Tønsberg, Norway.
authors.forename: Guro L
authors.initials: GL
authors.lastname: Andersen
mesh_terms: D002547:Cerebral Palsy / Q000175:diagnosis* / Q000453:epidemiology*; D002648:Child; D005260:Female; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D009664:Norway / Q000453:epidemiology; D015995:Prevalence; D012042:Registries / Q000706:statistics & numerical data*; D012189:Retrospective Studies