Combining a budgetary-impact analysis and a cost-effectiveness analysis using decision-analytic modelling techniques

Background: Reimbursement of new drugs is usually based on the budgetary impact of a new drug but there is also increasing demand for cost-effectiveness data on new drugs. Objective: To present a modelling technique (methodology) for an appropriate assessment of the budgetary impact of a new drug, which can simultaneously be used for a traditional cost-effectiveness analysis. Design and perspective: To illustrate the methodology, a model was constructed for a new hypothetical drug in Parkinson's disease, which allowed us to determine the budgetary impact and the cost effectiveness of this new antiparkinsonian drug from a societal perspective. The methodology consisted of two steps: (i) a simple population model (Markov model) was constructed to validate the epidemiological data by proving the consistency between the prevalence and incidence of Parkinson's disease for the Dutch population; (ii) this model was extended to a more complex model (semi-Markov model) by incorporation of disease progression for Parkinson's disease and all relevant economic and clinical measures. These included all drug utilisation associated with Parkinson's disease, as well as other resource utilisation patterns associated with outpatient and inpatient care for the treatment of Parkinson's disease. Results: The study showed that the difference in epidemiological data between a simple model and a complex model are substantial, which justifies the development of a complex model with a higher external validity. The complex model allowed an assessment of all potential candidates for the new drug and simultaneously allowed the assessment of the cost effectiveness of the new drug versus usual care. Conclusion: One model can be used for an appropriate assessment of the budgetary impact and the cost effectiveness of a new drug.