Economic evaluation of rivastigmine in patients with Parkinson’s disease dementia
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Background: The positive results of a randomised clinical trial of rivastigmine in patients with dementia associated with Parkinson’s disease have been published recently. Patient-level healthcare utilisation data were also collected, and this report is the economic evaluation based on these data.
Objective: To determine the cost effectiveness of rivastigmine 3–12 mg/day in patients in whom mild to moderate dementia developed at least 2 years after they received a clinical diagnosis of Parkinson’s disease.
Methods: A cost-effectiveness analysis was performed by applying Canadian and UK cost weights (year 2004 values) to healthcare utilisation data collected prospectively during a randomised, double-blind, multinational, 24-week trial of rivastigmine 3.12 mg/day (n = 362) versus placebo (n = 179). Patients were ≥50 years of age, had a Mini-Mental State Examination (MMSE) score of between 20 and 24 and had contact with a responsible caregiver at least 3 days a week.
Quality-adjusted survival time, transformed from MMSE scores, was the measure of effectiveness. Caregiver costs included paid and unpaid time, and direct costs included concomitant medications, outpatient care, hospitalisations, long-term care and study medications. Analysis was conducted from a societal perspective with a time horizon of 24 weeks.
Results: Consistent with the improvement in clinical outcomes, there was an observed increase in quality-adjusted survival time in the rivastigmine arm of 2.81 quality-adjusted life-days (two-sided p-value 0.13 [90% CI −0.243, 5.86]). Using Canadian price weights, there was an observed increase in cost in the rivastigmine arm of $Can55.76 (two-sided p-value 0.98 [90% CI −3431, 3543]), with a resulting incremental cost-effectiveness ratio of $Can7429 per QALY. Using UK price weights, there was an observed decrease in cost in the rivastigmine arm of £26.18 (two-sided p-value 0.99 [90% CI −2407, 2355]).
Conclusion: Although no between-treatment differences in cost were seen, the small sample size, highly variable cost distributions and short time horizon prevent us from making strong conclusions with regard to the effect of rivastigmine on total costs and, by inference, on cost effectiveness.
KeywordsUtility Score Rivastigmine MMSE Score Caregiver Time Price Weight
Andrew Willan provided the overall supervision of the cost-effectiveness evaluation project, provided the direct supervision of the statistical analysis, and wrote the manuscript. Ron Goeree provided the direct supervision of the collection of price weights and wrote the corresponding sections of the manuscript. Eleanor Pullenayegum performed the statistical analysis and reviewed and made edits to the manuscript. Christopher McBurney supervised the conduct of the cost component of the EXPRESS (EXelon in PaRkinson’s disEaSe dementia Study) trial and reviewed and made edits to the manuscript. Gordon Blackhouse collected the Canadian price weights and merged these and the UK price weights with the utilisation data to determine the cost for individual patients. Dr Blackhouse also reviewed and made edits to the manuscript. The authors wish to thank Ms Susan Tomlinson and Ms Sara Quirk for their meticulous proofreading. Of course, all remaining errors are the authors’ own responsibility. The authors also wish to thank the editor and reviewers for their many helpful comments, which have led to a greatly improved manuscript.
Andrew Willan is funded through the Discovery Grant Program of the Natural Sciences and Engineering Research Council of Canada (grant number 44868-03) and Eleanor Pullenayegum is supported through a studentship by the Ontario Student Opportunity Trust Fund — Hospital for Sick Children Foundation Student Scholarship Program; however, the opinions expressed are those of the authors and should not be attributed to any funding agency. Funding support for the research reported in this article was received from Novartis. Dr McBurney is an employee of Novartis and owns stock in the company.
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