In a cost-effectiveness plane, which quadrant represents a treatment that is more effective and cheaper?

• A. Upper left (more effective and cheaper)
• B. Upper right (more effective but more expensive)
• C. Lower left (less effective and cheaper)
• D. Lower right (more effective and cheaper)

Answer: (D)

A treatment that is more effective and cheaper dominates the comparator. On the cost-effectiveness plane, this means you move to the quadrant where the incremental cost is negative (cost goes down) and the incremental effect is positive (effect goes up). In the common layout, with cost differences on the horizontal axis (left is cheaper) and effect differences on the vertical axis (up is more effective), this region is the upper left quadrant. So the best choice is the quadrant where you gain more health benefit while spending less money. The other quadrants reflect scenarios where costs and effects move in the same or opposite directions that don’t combine to a clear dominance. If your diagram uses a different axis orientation, the exact quadrant may look different, but the principle—more effect and lower cost—remains the same.