If ICER is calculated as (Cost A − Cost B) / (Effect A − Effect B), what does a higher ICER imply?

• A. The extra cost per additional unit of effect is higher.
• B. The intervention is less costly per unit of effect.
• C. There is no difference in outcomes.
• D. The intervention is always cost-effective.

Answer: (C)

The main idea is that ICER tells you how much extra money you must spend to gain one additional unit of health effect when moving from one option to another. A higher ICER means you’re paying more for each extra unit of effect, so the choice is less cost-effective at a given willingness-to-pay threshold. If there’s no difference in outcomes, the denominator is zero and the ICER is undefined, which isn’t described by a higher ICER. The other interpretations—being less costly per unit of effect, there being no difference, or being always cost-effective—don’t align with the meaning of a higher ICER.