title: Scleroderma prevalence: demographic variations in a population-based sample.
abstract: OBJECTIVE
  To estimate the prevalence of systemic sclerosis (SSc) using population-based administrative data, and to assess the sensitivity of case ascertainment approaches.
  
  
  METHODS
  We ascertained SSc cases from Quebec physician billing and hospitalization databases (covering approximately 7.5 million individuals). Three case definition algorithms were compared, and statistical methods accounting for imperfect case ascertainment were used to estimate SSc prevalence and case ascertainment sensitivity. A hierarchical Bayesian latent class regression model that accounted for possible between-test dependence conditional on disease status estimated the effect of patient characteristics on SSc prevalence and the sensitivity of the 3 ascertainment algorithms.
  
  
  RESULTS
  Accounting for error inherent in both the billing and the hospitalization data, we estimated SSc prevalence in 2003 at 74.4 cases per 100,000 women (95% credible interval [95% CrI] 69.3-79.7) and 13.3 cases per 100,000 men (95% CrI 11.1-16.1). Prevalence was higher for older individuals, particularly in urban women (161.2 cases per 100,000, 95% CrI 148.6-175.0). Prevalence was lowest in young men (in rural areas, as low as 2.8 cases per 100,000, 95% CrI 1.4-4.8). In general, no single algorithm was very sensitive, with point estimates for sensitivity ranging from 20-73%.
  
  
  CONCLUSIONS
  We found marked differences in SSc prevalence according to age, sex, and region. In general, no single case ascertainment approach was very sensitive for SSc. Therefore, using data from multiple sources, with adjustment for the imperfect nature of each, is an important strategy in population-based studies of SSc and similar conditions.
authors.affiliation: Division of Clinical Epidemiology, McGill University Health Centre, Montreal, Quebec, Canada. sasha.bernatsky@mail.mcgill.ca
authors.forename: S
authors.initials: S
authors.lastname: Bernatsky
authors.forename: L
authors.initials: L
authors.lastname: Joseph
authors.forename: C A
authors.initials: CA
authors.lastname: Pineau
authors.forename: P
authors.initials: P
authors.lastname: Belisle
authors.forename: M
authors.initials: M
authors.lastname: Hudson
authors.forename: A E
authors.initials: AE
authors.lastname: Clarke
mesh_terms: D000328:Adult; D017677:Age Distribution; D000465:Algorithms; D001499:Bayes Theorem; D016208:Databases, Factual; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D038801:International Classification of Diseases; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011792:Quebec / Q000453:epidemiology; D012594:Scleroderma, Localized / Q000453:epidemiology*; D012595:Scleroderma, Systemic / Q000453:epidemiology*; D017678:Sex Distribution