Severity-Adjusted Probability of Being Cost Effective

Background In the context of priority setting, a diferential cost-efectiveness threshold can be used to refect a higher societal willingness to pay for quality-adjusted life-year gains in the worse of. However, uncertainty in the estimate of severity can lead to problems when evaluating the outcomes of cost-efectiveness analyses. Objectives This study standardizes the assessment of severity, integrates its uncertainty with the uncertainty in cost-efectiveness results and provides decision makers with a new estimate: the severity-adjusted probability of being cost efective. Methods Severity is expressed in proportional and absolute shortfall and estimated using life tables and country-specifc EQ-5D values. We use the three severity-based cost-efectiveness thresholds (€20.000, €50.000 and €80.000, per QALY) adopted in The Netherlands. We exemplify procedures of integrating uncertainty with a stylized example of a hypothetical oncology treatment. Results Applying our methods, taking into account the uncertainty in the cost-efectiveness results and in the estimation of severity identifes the likelihood of an intervention being cost efective when there is uncertainty about the appropriate severity-based cost-efectiveness threshold. Conclusions Higher willingness-to-pay thresholds for severe diseases are implemented in countries to refect societal concerns for an equitable distribution of resources. However, the estimates of severity are uncertain, patient populations are heterogeneous, and this can be accounted for with the severity-adjusted probability of being cost efective proposed in this study. The application to the Netherlands suggests that not adopting the new method could result in incorrect decisions in the reimbursement of new health technologies