Estimating chronic disease rates in Canada: which population-wide denominator to use? / Taux de maladies chroniques au Canada : quel dénominateur utiliser pour l'estimation de l'ensemble de la population?

INTRODUCTION: Chronic disease rates are produced from the Public Health Agency of Canada's Canadian Chronic Disease Surveillance System (CCDSS) using administrative health data from provincial/territorial health ministries. Denominators for these rates are based on estimates of populations derived from health insurance files. However, these data may not be accessible to all researchers. Another source for population size estimates is the Statistics Canada census. The purpose of our study was to calculate the major differences between the CCDSS and Statistics Canada's population denominators and to identify the sources or reasons for the potential differences between these data sources. METHODS: We compared the 2009 denominators from the CCDSS and Statistics Canada. The CCDSS denominator was adjusted for the growth components (births, deaths, emigration and immigration) from Statistics Canada's census data. RESULTS: The unadjusted CCDSS denominator was 34 429 804, 3.2% higher than Statistics Canada's estimate of population in 2009. After the CCDSS denominator was adjusted for the growth components, the difference between the two estimates was reduced to 431 323 people, a difference of 1.3%. The CCDSS overestimates the population relative to Statistics Canada overall. The largest difference between the two estimates was from the migrant growth component, while the smallest was from the emigrant component. CONCLUSION: By using data descriptions by data source, researchers can make decisions about which population to use in their calculations of disease frequency.

INTRODUCTION: Les taux de maladies chroniques du Système canadien de surveillance des maladies chroniques (SCSMC) de l'Agence de la santé publique du Canada sont fondés sur les données administratives sur la santé fournies par les ministères de la Santé des provinces et des territoires. Les dénominateurs utilisés pour calculer ces taux reposent sur des estimations de population tirées des dossiers d'assurance-maladie, données toutefois pas systématiquement accessibles à tous les chercheurs. Le recensement de Statistique Canada constitue quant à lui une autre source d'estimation de la taille de la population. Notre étude visait d'abord à calculer les principaux écarts entre les dénominateurs de population à partir des estimations du SCSMC et à partir de celles de Statistique Canada et ensuite à déterminer les causes à l'origine des écarts entre ces sources de données. MÉTHODOLOGIE: Nous avons comparé pour 2009 les dénominateurs fournis par le SCSMC et ceux fournis par Statistique Canada. Le dénominateur du SCSMC a été ajusté pour tenir compte des composantes de la croissance (naissances, décès, émigrants et immigrants) tirées des données de recensement de Statistique Canada. RÉSULTATS: Le dénominateur non ajusté du SCSMC était de 34 429 804 personnes, soit une différence de + 3,2 % par rapport à l'estimation de population de Statistique Canada pour 2009. Après ajustement du dénominateur du SCSMC pour tenir compte des composantes de la croissance, la différence entre les deux estimations s'est trouvé réduite à 431 323 personnes, soit un écart de 1,3 %. L'estimation tirée du SCSMC constitue une surestimation par rapport à celle de Statistique Canada. Le plus grand écart entre les deux estimations relève de la composante de croissance liée à l'immigration, alors que l'écart le moindre provient de la composante de croissance liée à la population émigrante. CONCLUSION: Disposant des descriptions de données par source de données, les chercheurs peuvent choisir quelle estimation de la population utiliser dans leurs calculs des fréquences de maladies.

Comparison of the estimated prevalence of mood and/or anxiety disorders in Canada between self-report and administrative data.

BACKGROUND: To compare trends in the estimated prevalence of mood and/or anxiety disorders identified from two data sources (self-report and administrative). Reviewing, synthesising and interpreting data from these two sources will help identify potential factors that underlie the observed estimates and inform public health action. METHOD: We used self-reported, diagnosed mood and/or anxiety disorder cases from the Canadian Community Health Survey (CCHS) across a 5-year span (from 2003 to 2009) to estimate the prevalence among the Canadian population aged ≥15 years. We also estimated the prevalence of mood and/or anxiety disorders using the Canadian Chronic Disease Surveillance System (CCDSS), which identified cases using ICD-9/-10-CA codes from physician billing claims and hospital discharge records during the same time period. The prevalence rates for mood and/or anxiety disorders were compared across the CCHS and CCDSS by age and sex for all available years of data from 2003 to 2009. Summary rates were age-standardised to the Canadian population as of 1 October 1991. RESULTS: In 2009, the prevalence of mood and/or anxiety disorders was 9.4% using self-reported data v. 11.3% using administrative data. Prevalence rates obtained from administrative data were consistently higher than those from self-report for both men and women. However, due to an increase in the prevalence of self-reported cases, these differences decreased over time (rate ratios for both sexes: 1.6-1.2). Prevalence estimates were consistently higher among females compared with males irrespective of data source. While differences in the prevalence estimates between the two data sources were evident across all age groups, the reduction of these differences was greater among adolescent, young and middle-aged adults compared with those 70 years and older. CONCLUSIONS: The overall narrowing of differences over time reflects a convergence of information regarding the prevalence of mood and/or anxiety disorders trends between self-report and administrative data sources. While the administrative data-based prevalences remained relatively stable, the self-reported prevalences increased over time. These observations may reflect positive societal changes in the perceptions of mental health (declining stigma) and/or increasing mental health literacy. Additional research using non-ecological data is required to further our understanding of the observed findings and trends, including a data linkage exercise permitting a comparison of prevalence estimates and population characteristics from these two data sources both separately and merged.

Validation of diabetes case definitions using administrative claims data.

AIMS: Our aim was to validate three diabetes case definitions for children and adolescents aged <20 years in Canada using administrative and clinical data in the province of British Columbia. METHODS: We identified potential cases of diabetes from physician claims, hospitalizations and prescription drug records between 1992/1993 and 2007/2008 using the three different case definitions, which included a national standard as well as two regionally developed case definitions. Each case definition used a different combination of administrative data; however, only one definition used prescription drug records. The sensitivity of each definition was calculated against the 'gold standard' of diagnosed cases recorded in British Columbia's Children's Hospital Endocrinology and Diabetes Unit clinical database. RESULTS: During this time period, 2611 patients were seen at the British Columbia's Children's Hospital. The sensitivities (95% CIs) of the national and two regional case definitions were 0.95 (0.941-0.958), 0.97 (0.964-0.977) and 0.82 (0.800-0.830), respectively. CONCLUSIONS: Our results highlight the benefit of regional case definitions that exploit the availability of different data sources, but also support that a nationally derived definition is sensitive among children and adolescents.