title: The application of current lifetable methods to compare cystic fibrosis median survival internationally is limited.
abstract: BACKGROUND
  Comparing international estimates of survival can be a useful way of highlighting differences in life expectancy between cystic fibrosis (CF) populations. In this study, we compared survival in two CF populations.
  
  
  METHODS
  The current lifetable method takes age-specific mortality rates observed in a given year and applies them to a hypothetical population assuming those rates will remain the same in the future. This was used to compare median predicted survival in the United States (US) and the Republic of Ireland (RoI) (1986-2008). Median age at death among decedents was also examined.
  
  
  RESULTS
  In both countries, median age at death was lower than median predicted survival. Successive increases in annual median predicted survival were not observed; rather an overall improvement was discerned over time. In the RoI, where absolute numbers of deaths were small, year-on-year fluctuations in age-specific mortality rates resulted in wide-ranging annual median predicted survival estimates.
  
  
  CONCLUSIONS
  Median age at death is not a good measure of CF survival. Though median predicted survival improved in each country over the study period, between-country comparison at a given time point may be misleading for rare disorders like CF. Longitudinal outcomes must be examined.
authors.affiliation: UCD School of Public Health, Physiotherapy and Population Science, Woodview House, University College Dublin, Belfield, Dublin 4, Ireland. abaigeal.jackson@ucd.ie
authors.forename: Abaigeal D
authors.initials: AD
authors.lastname: Jackson
authors.forename: Leslie
authors.initials: L
authors.lastname: Daly
authors.forename: Cecily
authors.initials: C
authors.lastname: Kelleher
authors.forename: Bruce C
authors.initials: BC
authors.lastname: Marshall
authors.forename: Hebe B
authors.initials: HB
authors.lastname: Quinton
authors.forename: Linda
authors.initials: L
authors.lastname: Foley
authors.forename: Patricia
authors.initials: P
authors.lastname: Fitzpatrick
mesh_terms: D003550:Cystic Fibrosis / Q000453:epidemiology*; D006801:Humans; D007494:Ireland; D008017:Life Expectancy; D015993:Life Tables; D009026:Mortality; D012042:Registries; D016019:Survival Analysis; D015996:Survival Rate; D014481:United States