title: Country to country variation: what can be learnt from national cystic fibrosis registries.
abstract: OBJECTIVE
  This review will address the evolving science involving international comparisons of populations of persons living with cystic fibrosis. Understanding the current clinical outcomes in cystic fibrosis is critical prior to assessing such comparisons. Countries that differ in clinical approaches provide natural experiments to assess those approaches.
  
  
  RESULTS
  Recent studies have highlighted that the population of persons with cystic fibrosis is changing; estimates predict a continued growth of cystic fibrosis populations with substantial increases in persons with cystic fibrosis who are adults. Additional work highlighted differences in subpopulations (i.e. children); US cystic fibrosis children appear to have better lung function, but similar nutritional status, compared to UK cystic fibrosis children. These differences were associated with differences in intensity of care, with a higher proportion of US children receiving more cystic fibrosis-specific therapies. Additional research raises important questions regarding potential sampling bias in different patient registries and differing rates of unconfirmed cases of cystic fibrosis. These and other limitations are highlighted.
  
  
  CONCLUSIONS
  Differences in both demographics and clinical outcomes in cystic fibrosis between nations can be informative, but, like many types of observational research, are at risk of unrecognized bias. Despite this limitation, these comparisons can lead to substantive improvements in care in cystic fibrosis.
authors.affiliation: Department of Medicine Department of Pediatrics, University of Washington, Seattle, Washington, USA.
authors.forename: Christopher Hooper
authors.initials: CH
authors.lastname: Goss
mesh_terms: D003550:Cystic Fibrosis / Q000453:epidemiology; D006801:Humans; D009752:Nutritional Status; D012042:Registries