Introduction: As the population ages and the prevalence of comorbid conditions increases, the need for feasible, validated methods of comorbidity surveillance in chronic diseases such as multiple sclerosis ( MS ) increases.

Methods: Using kappa (k) statistics, we evaluated the performance of administrative case definitions for comorbidities commonly observed in MS by comparing agreement between Manitoba ( MB ) administrative data and self-report (n = 606) and Nova Scotia (NS) administrative data and self-report (n = 1923).

Results: Agreement between the administrative definitions and self-report was substantial for hypertension (k = 0.69 [NS], 0.76 [ MB ]) and diabetes (k = 0.70 [NS], 0.66 [ MB ]); moderate for hyperlipidemia (k = 0.53 [NS], 0.51 [ MB ]) and heart disease (k = 0.42 [NS], 0.51 [ MB ]) and fair for anxiety (k = 0.27 [NS], 0.26 [ MB ]). In NS, agreement was substantial for inflammatory bowel disease (k = 0.71) and moderate for epilepsy (k = 0.48).

Conclusion: Administrative definitions for commonly observed comorbidities in MS performed well in 2 distinct jurisdictions. This suggests that they could be used more broadly across Canada and in national studies.