Rheumatoid arthritis prevalence in Quebec
BMC Research Notes
Rheumatoid arthritis prevalence in Quebec
Sasha Bernatsky 0 1
Alaa Dekis 0
Marie Hudson 2
Christian A Pineau 0
Gilles Boire 6
Paul R Fortin 5
Louis Bessette 4 5
Sonia Jean 3
Ann L Chetaille 5
Patrick Belisle 1
Louise Bergeron 8
Debbie Ehrmann Feldman 7
Lawrence Joseph 1
0 Division of Rheumatology, McGill University Health Centre , Montreal, Quebec , Canada
1 Division of Clinical Epidemiology, McGill University Health Centre , 687 Pine Avenue West, V-Building, V2.09, Montreal, QC H3A 1A1 , Canada
2 Jewish General Hospital and Lady David Research Institute , Montreal, Quebec , Canada
3 Chronic Disease Surveillance Division, National Institute of Public Health of Québec , Quebec City, Quebec , Canada
4 Rheumatology Department, Centre Hospitalier Universitaire de Québec (CHUQ) Research Centre , Quebec City, Quebec , Canada
5 Faculty of Medicine, Laval University , Quebec City, Quebec , Canada
6 Department of Medicine, University of Sherbrooke , Sherbrooke, Quebec , Canada
7 Université de Montréal, École de réadaptation , Montreal, Quebec , Canada
8 Canadian Arthritis Patient Alliance , Ile Perrot, Quebec , Canada
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.
Arthritis; Epidemiology; Rheumatoid Arthritis
Background
There is growing interest in developing tools and
methods for the surveillance of chronic rheumatic
diseases, using existing resources such as administrative
health databases. Comparing disease prevalence across
certain regions might be of particular interest; for
example, for historic and geographic reasons, individuals
in some rural regions of Quebec have been somewhat
isolated from other parts of the province. This has many
potential effects; one may be differences in genetic
make-up, and other may be variations in access to care.
Differences in access to care might mean that the
sensitivity and specificity of administrative data-based
case definitions may vary across rural versus urban
areas, and even within rural areas, from one sub-region
to another.
Our objective was to estimate the prevalence of
rheumatoid arthritis (RA) in Quebec based on
administrative health data, and to determine if RA prevalence
estimates were any different in urban versus rural
regions. We also performed exploratory sub-analyses in
two regions which have been particularly isolated
geographically. Since administrative data rely on medical
contact in order to ascertain cases, the RA prevalence
estimates in these very isolated areas (where access to
care is presumably lower) might be different from the
rest of rural Quebec. On the other hand, very isolated
regions generally tend to have reduced genetic variation
[
1-3
] which theoretically could alter RA risk (compared
to the rest of Quebec), since genetic susceptibility is a
risk factor (albeit a complex one) for RA [
4
]. We sought
to provide new data regarding the estimates of RA
prevalence across regions in Quebec, including these
very isolated regions. The methodological approach
chosen in this paper offers a means of dealing with the
imperfect nature of administrative data, as will be seen.
Methods
We used hospitalization and physician billing data for all
of Quebec (approximately 7.6 million residents), across
1992–2008, to estimate the prevalence of existing RA
cases in 2008. The data include hospitalization discharge
diagnoses (...truncated)