In economic evaluations, which graphical/probabilistic tool shows how the probability of cost-effectiveness changes with willingness-to-pay?

• A. ICER curve
• B. CEAC
• C. Cost-effectiveness plane
• D. WTP curve

Answer: (B)

The Cost-Effectiveness Acceptability Curve shows how the probability that an intervention is cost-effective changes as willingness-to-pay (WTP) for an extra unit of effect varies. It comes from probabilistic sensitivity analysis: for each simulated parameter set, you compute the net monetary benefit at each WTP value (NMB = WTP × ΔEffect − ΔCost). The fraction of simulations with positive NMB at a given WTP gives the probability that the intervention is cost-effective at that threshold, and plotting these probabilities across a range of WTP values yields the curve. This curve helps you see how robust the cost-effectiveness conclusion is as decision-makers’ WTP changes and to identify thresholds where cost-effectiveness is likely.

In contrast, the cost-effectiveness plane is a scatter plot of incremental costs versus incremental effects and shows uncertainty around the estimate, but it does not provide a probability of cost-effectiveness as a function of WTP. The other terms aren’t standard tools for depicting how likelihood changes with WTP.