Abstract
To validate a case definition of multiple sclerosis (MS) using health administrative data and to provide the first province-wide estimates of MS incidence and prevalence for Saskatchewan, Canada. We used population-based health administrative data between January 1, 1996 and December 31, 2015 to identify individuals with MS using two potential case definitions: (1) ≥3 hospital, physician, or prescription claims (Marrie definition); (2) ≥1 hospitalization or ≥5 physician claims within 2 years (Canadian Chronic Disease Surveillance System [CCDSS] definition). We validated the case definitions using diagnoses from medical records (n=400) as the gold standard. The Marrie definition had a sensitivity of 99.5% (95% confidence interval [CI] 92.3-99.2), specificity of 98.5% (95% CI 97.3-100.0), positive predictive value (PPV) of 99.5% (95% CI 97.2-100.0), and negative predictive value (NPV) of 97.5% (95% CI 94.4-99.2). The CCDSS definition had a sensitivity of 91.0% (95% CI 81.2-94.6), specificity of 99.0% (95% CI 96.4-99.9), PPV of 98.9% (95% CI 96.1-99.9), and NPV of 91.7% (95% CI 87.2-95.0). Using the more sensitive Marrie definition, the average annual adjusted incidence per 100,000 between 2001 and 2013 was 16.5 (95% CI 15.8-17.2), and the age- and sex-standardized prevalence of MS in Saskatchewan in 2013 was 313.6 per 100,000 (95% CI 303.0-324.3). Over the study period, incidence remained stable while prevalence increased slightly. We confirm Saskatchewan has one of the highest rates of MS in the world. Similar to other regions in Canada, incidence has remained stable while prevalence has gradually increased.
Highlights
With ~100,000 affected individuals, Canada has one of the highest rates of multiple sclerosis (MS) in the world.[1]
Agreement between the clinical and administrative cohorts was high with a κ of 0.97 for the Marrie definition and 0.90 for the Chronic Disease Surveillance System (CCDSS) definition
The age at which prevalence peaked increased over time (Figure 3). The results of this first-ever province-wide examination of incidence and prevalence confirm that Saskatchewan has one of the highest rates of MS in Canada, and worldwide
Summary
With ~100,000 affected individuals, Canada has one of the highest rates of multiple sclerosis (MS) in the world.[1] Despite the high prevalence, precise estimates of epidemiology are missing for some Canadian regions. The etiology of MS remains elusive but evidence suggests geographic and environmental factors, including genetic heterogeneity, may play an important role.[2]. From the College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, SK, Canada (LHA, DFB, CDE); Departments of Internal Medicine and Community Health Sciences, University of Manitoba, Winnipeg, MB, Canada (RAM); College of Medicine (Physical Medicine and Rehabilitation), University of Saskatchewan, Saskatoon, SK, Canada (KBK). IP address: 52.87.161.73, on 02 Nov 2021 at 12:00:53, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms
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