What does the cost-effectiveness plane graphically display?

• A. Differences in patient satisfaction between interventions.
• B. The geographic distribution of costs.
• C. Differences in cost and effectiveness between interventions.
• D. The discount rates used in the analysis.

Answer: (C)

The cost-effectiveness plane is a visual way to show the trade-off between cost and effectiveness when comparing two interventions. It’s a scatter plot where the horizontal axis represents incremental cost (cost difference between the new intervention and the comparator) and the vertical axis represents incremental effectiveness (usually measured in QALYs gained). Each point represents a possible estimate of those differences, illustrating uncertainty around both cost and effect.

This setup lets you see where the new intervention sits in terms of cost and benefit: more costly but more effective, cheaper but less effective, or somewhere in between across the four quadrants. It also helps assess how often the intervention is cost-effective at different willingness-to-pay thresholds. In short, it graphically displays differences in cost and effectiveness between interventions. It’s not a map of patient satisfaction, geographic cost patterns, or discount rates.