title: Rheumatoid arthritis prevalence in Quebec.
abstract: BACKGROUND
  To estimate rheumatoid arthritis (RA) prevalence in Quebec using administrative health data, comparing across regions.
  
  
  METHODS
  Cases of RA were ascertained from physician billing and hospitalization data, 1992-2008. We used three case definitions: 1) ≥ 2 billing diagnoses, submitted by any physician, ≥ 2 months apart, but within 2 years; 2) ≥ 1 diagnosis, by a rheumatologist; 3) ≥1 hospitalization diagnosis (all based on ICD-9 code 714, and ICD-10 code M05). We combined data across these three case definitions, using Bayesian hierarchical latent class models to estimate RA prevalence, adjusting for the imperfect sensitivity and specificity of the data. We compared urban versus rural regions.
  
  
  RESULTS
  Using our case definitions and no adjustment for error, we defined 75,760 cases for an over-all RA prevalence of 9.9 per thousand residents. After adjusting for the imperfect sensitivity and specificity of our case definition algorithms, we estimated Quebec RA prevalence at 5.6 per 1000 females and 4.1 per 1000 males. The adjusted RA prevalence estimates for older females were the highest for any demographic group (9.9 cases per 1,000), and were similar in rural and urban regions. In younger males and females, and in older males, RA prevalence estimates were lower in rural versus urban areas.
  
  
  CONCLUSIONS
  Without adjustment for error inherent in administrative databases, RA prevalence in Quebec was approximately 1%, while adjusted estimates are approximately half that. The lower prevalence in rural areas, seen for most demographic groups, may suggest either true regional variations in RA risk, or under-ascertainment of cases in rural Quebec.
authors.affiliation: Division of Clinical Epidemiology, McGill University Health Centre, 687 Pine Avenue West, V-Building, V2.09, Montreal, QC, H3A 1A1, Canada. sasha.bernatsky@mcgill.ca.|Division of Rheumatology, McGill University Health Centre, Montreal, Quebec, Canada. sasha.bernatsky@mcgill.ca.
authors.forename: Sasha
authors.initials: S
authors.lastname: Bernatsky
authors.affiliation: Division of Rheumatology, McGill University Health Centre, Montreal, Quebec, Canada. alaa.dekis@mail.mcgill.ca.
authors.forename: Alaa
authors.initials: A
authors.lastname: Dekis
authors.affiliation: Jewish General Hospital and Lady David Research Institute, Montreal, Quebec, Canada. marie.hudson@mcgill.ca.
authors.forename: Marie
authors.initials: M
authors.lastname: Hudson
authors.affiliation: Division of Rheumatology, McGill University Health Centre, Montreal, Quebec, Canada. christian.pineau@mcgill.ca.
authors.forename: Christian A
authors.initials: CA
authors.lastname: Pineau
authors.affiliation: Department of Medicine, University of Sherbrooke, Sherbrooke, Quebec, Canada. gilles.boires@usherbrooke.ca.
authors.forename: Gilles
authors.initials: G
authors.lastname: Boire
authors.affiliation: Faculty of Medicine, Laval University, Quebec City, Quebec, Canada. paul.fortin@crchuq.ulaval.ca.
authors.forename: Paul R
authors.initials: PR
authors.lastname: Fortin
authors.affiliation: Faculty of Medicine, Laval University, Quebec City, Quebec, Canada. louis.bessette@crchul.ulaval.ca.|Rheumatology Department, Centre Hospitalier Universitaire de Québec (CHUQ) Research Centre, Quebec City, Quebec, Canada. louis.bessette@crchul.ulaval.ca.
authors.forename: Louis
authors.initials: L
authors.lastname: Bessette
authors.affiliation: Chronic Disease Surveillance Division, National Institute of Public Health of Québec, Quebec City, Quebec, Canada. sonia.jean@inspq.qc.ca.
authors.forename: Sonia
authors.initials: S
authors.lastname: Jean
authors.affiliation: Faculty of Medicine, Laval University, Quebec City, Quebec, Canada. anne-laure.chetaille@mail.chuq.qc.ca.
authors.forename: Ann L
authors.initials: AL
authors.lastname: Chetaille
authors.affiliation: Division of Clinical Epidemiology, McGill University Health Centre, 687 Pine Avenue West, V-Building, V2.09, Montreal, QC, H3A 1A1, Canada. patrick.belisle@clinepi.mcgill.ca.
authors.forename: Patrick
authors.initials: P
authors.lastname: Belisle
authors.affiliation: Canadian Arthritis Patient Alliance, Ile Perrot, Quebec, Canada. louise383@sympatico.ca.
authors.forename: Louise
authors.initials: L
authors.lastname: Bergeron
authors.affiliation: Université de Montréal, École de réadaptation, Montreal, Quebec, Canada. debbie.feldman@umontreal.ca.
authors.forename: Debbie Ehrmann
authors.initials: DE
authors.lastname: Feldman
authors.affiliation: Division of Clinical Epidemiology, McGill University Health Centre, 687 Pine Avenue West, V-Building, V2.09, Montreal, QC, H3A 1A1, Canada. lawrence.joseph@mcgill.ca.
authors.forename: Lawrence
authors.initials: L
authors.lastname: Joseph
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000453:epidemiology*; D001499:Bayes Theorem; D005260:Female; D006306:Health Surveys / Q000379:methods / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007344:Insurance Claim Reporting / Q000706:statistics & numerical data; D038801:International Classification of Diseases / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D009819:Office Visits / Q000706:statistics & numerical data; D010351:Patient Discharge / Q000706:statistics & numerical data; D015995:Prevalence; D011792:Quebec / Q000453:epidemiology; D015203:Reproducibility of Results; D012423:Rural Health / Q000706:statistics & numerical data*; D014504:Urban Health / Q000706:statistics & numerical data*