Scenario analysis when conducting budget impact analyses for rare diseases

Pharmacoeconomic analyses are an important and useful guide for understanding a pharmacotherapeutic intervention's financial impact for relevant stakeholders. One type of pharmacoeconomic analysis that assesses a pharmacotherapeutic intervention's short-term financial implications is a budget impact analysis. Although methodology guidelines for budget impact analyses in the United States currently exist, not much guidance is available for analyses that are being conducted of rare or ultrarare disease states. In this article, we propose conducting a scenario analysis for pharmacotherapeutic interventions to treat rare diseases by varying health plan sizes to indicate what the potential plan impact would be if 1 member in said health plan received treatment. We then walk through an illustrative example and discuss the rationale for it.