title: Children with hemodynamically significant congenital heart disease can be identified through population-based registers.
abstract: BACKGROUND
  Epidemiological research is facilitated in Sweden by a history of national health care registers, making large unselected national cohort studies possible. However, for complex clinical populations, such as children with congenital heart disease (CHD), register-based studies are challenged by registration limitations. For example, the diagnostic code system International Classification of Diseases, 10th version (ICD-10) does not indicate the clinical significance of abnormalities, therefore may be of limited use if used as the sole parameter in epidemiological research. Palivizumab is indicated as a prophylactic treatment against respiratory syncytial virus infections in children with hemodynamically significant CHD.
  
  
  OBJECTIVE
  The aim of the study reported here was to develop and validate an algorithm to identify children with hemodynamically significant CHD according to recommendations for palivizumab prophylaxis in register-based research.
  
  
  METHODS
  By using a strategy of combining criteria for age at diagnosis, diagnostic codes, surgical procedure codes, and dispensing records, we created an algorithm to define the specific cases with hemodynamically significant CHD in which palivizumab could be advocated according to recommendations.
  
  
  RESULTS
  The algorithm identified 928 children with hemodynamically significant CHD in the Swedish birth cohort born July 1, 2005 to December 31, 2010. A sensitivity (95% confidence interval) of 80% (70-88) for the algorithm was found by analyzing 121 children identified through local hospital data who were treated with palivizumab within a defined region and study period. The positive predictive value was estimated by medical record review in a random sample of 34 cases identified by the algorithm. In 79% (62-91) of these cases, the children were regarded as having hemodynamically significant CHD according to the recommendations for treatment with palivizumab.
  
  
  CONCLUSIONS
  It was possible to identify a subgroup of children with hemodynamically significant CHD using an epidemiological approach and an algorithm with high validity. Our results will enable well-powered national cohort studies of individuals with complex clinical conditions such as hemodynamically significant CHD.
authors: Department of Women's and Children's Health, Solna, Karolinska Institutet, Stockholm, Sweden ; Centre for Pharmacoepidemiology, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden.
authors: Gunnar
authors: G
authors: Bergman
authors: The Child and Adolescent Clinic 4072, The Danish National University Hospital Rigshospitalet, Copenhagen, Denmark.
authors: Ann
authors: A
authors: Hærskjold
authors: The Child and Adolescent Clinic 4072, The Danish National University Hospital Rigshospitalet, Copenhagen, Denmark.
authors: Lone Graff
authors: LG
authors: Stensballe
authors: Centre for Pharmacoepidemiology, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden.
authors: Helle
authors: H
authors: Kieler
authors: Centre for Pharmacoepidemiology, Department of Medicine, Solna, Karolinska Institutet, Stockholm, Sweden.
authors: Marie
authors: M
authors: Linder
keywords: algorithm; complex clinical conditions; epidemiology; national cohort studies; palivizumab; population-based registries
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