Health Services/Policy
Validation of a health system-focused morbidity score for the Canadian population Emmalin Buajitti* Emmalin Buajitti Laura Rosella
Background. Multimorbidity is an important determinant of health care need and complexity, and presents a growing challenge for single-payer health care systems such as Canada’s. Multimorbidity measurement in Canada has historically relied on equal- or mortality-based weighting of chronic conditions (e.g., Charlson index, number of chronic conditions). To better support health system planning and population health, we sought to create a health care utilization-driven morbidity score using multi-linked health administrative data.
Methods. Following the approach of the UK-based Cambridge Multimorbidity Score, we identified 23 common chronic conditions using outpatient and inpatient records for all Ontario residents since April 1992. For those alive in April 2022 (n=15,303,282), we identified 3 health system-relevant outcomes (number of primary care visits, unplanned hospitalization, and death) between April 2022 and March 2023. We used logistic regression and Poisson models to estimate outcome-specific coefficients, which we pooled to create a general-outcome weight for each condition. We compared the accuracy of our score to the original CMS using c-statistics for mortality and hospitalization.
Results. The 3 chronic conditions with the highest general-outcome weights were dementia (weight=2.11), substance use problems (1.77), and congestive heart failure (1.44). The condition weights and rank order were substantively different in Canada compared to the original CMS. The morbidity score slightly outperformed the original CMS in the Ontario population, with c-statistics of 0.880 and 0.807 for 1-year risk of death and hospitalization, respectively (CMS = 0.876 and 0.784).
Conclusion. Health system-focused morbidity scores accurately predict risk of death and hospitalization in a Canadian population. Locally-derived scores can support appropriate, context-driven health system planning and population health management.