Which statement about NNT is true?

• A. Lower NNT indicates a more effective treatment.
• B. Higher NNT indicates a more effective treatment.
• C. NNT equals the number needed to harm.
• D. NNT is independent of treatment effect size.

Answer: (A)

Understanding NNT hinges on how many patients need treatment to achieve one additional beneficial outcome. The smaller the NNT, the more effective the treatment, because you achieve that single favorable result with fewer people treated. NNT is the reciprocal of the absolute risk reduction (ARR), which is the difference between event rates without and with the treatment. A larger ARR means a bigger treatment effect and thus a smaller NNT; a small ARR yields a larger NNT. This is why a lower NNT indicates greater effectiveness. NNT is not the number needed to harm—that distinction belongs to NNH—and NNT depends on the size of the treatment effect, so it is not independent of effect size.