PS 1-8
ESTIMATING THE HEALTHCARE COSTS ATTRIBUTABLE TO WEST NILE VIRUS: A POPULATION-BASED MATCHED COHORT STUDY IN ONTARIO, CANADA
To determine incidence-based healthcare costs attributable to West Nile virus (WNV) from the healthcare payer perspective in Ontario, Canada.
Method:
We established a cohort of incident laboratory-confirmed WNV cases between 1 January 2002 and 31 December 2012 from Public Health Ontario Laboratory (PHOL) data. Confirmed cases were individually linked to health administrative data and matched to population controls (1:3) using a combination of hard-matching and propensity-score matching.
Phase-of-care approach was used to estimate phase-specific attributable costs for acute and long-term illness. Phases were 1) acute infection, 2) continuing care, and 3) final care prior to death. Joinpoint analysis showed the length of acute infection was 90 days and final care was 100 days. Final care was further differentiated as acute death (if a case died ≤30 days post-index date) and late death (>30 days post-index date with costs taken ≤100 days before death). Continuing care was assigned the remaining time. We stratified costs by age, sex, and healthcare resource use (e.g., hospitalizations, physician visits). Costs are reported in 2014 Canadian dollars, standardized to 10-days.
Results:
694 cases with confirmed WNV disease were identified in the PHOL dataset and individually linked to health administrative data. All cases were matched to population controls, with standardized differences <0.1. Mean age was 52.3±17.1 years, n=352 (50.7%) were female, overall mortality was 12.1%. No deaths were observed among cases <45 years. Mean follow-up time was 5.3 years.
Mean 10-day acute infection, continuing care, acute death, and late death attributable costs were $1,406 (95% CI: $1,124, $1,688), $177 ($71, $283), $4,509 ($1,819, $7,199) and $5,128 ($2,742, $7,515), respectively. Attributable costs were greatest for cases aged 65-84 years during acute infection, and greatest for cases 45-64 years in final care. Expected mean attributable 1-, 3-year costs were $17,508, and $30,392 per case, respectively (unadjusted for survival).
Conclusion:
WNV disease is associated with increased acute and long-term healthcare costs compared to population controls. This is the first study to estimate the cost-of-illness of WNV in Ontario using linked health administrative data. Results from this analysis will be used to evaluate the cost-effectiveness of WNV intervention strategies. High-quality studies are needed to understand the health system impact of emerging and vector-borne diseases, as they have been identified as an international public health research priority.