Which statement about NNT is true?

• A. The smaller the NNT, the more efficient the treatment (fewer patients must be treated to achieve one benefit)
• B. The larger the NNT, the better
• C. NNT measures adverse events risk
• D. NNT is unrelated to efficacy

Answer: (A)

NNT reflects how many patients need to be treated for one additional person to benefit within a defined time frame. The key idea is that NNT is calculated from the absolute risk reduction (the difference in event rates between treatment and control), and then NNT = 1 / ARR. Because a smaller ARR means you must treat many more people to gain a single benefit, a smaller NNT indicates a more efficient or more effective treatment in that context.

For example, if treatment lowers the event rate from 10% to 4%, the ARR is 6% (0.06), so NNT is about 17. Treating 17 people yields one additional benefit. If another treatment only lowers the rate from 10% to 9%, the ARR is 1% (0.01), and the NNT is 100—less efficient.

The other statements aren’t correct: NNT does not measure adverse events risk (that would be NNH). A larger NNT is not better; it means you must treat more people to achieve one benefit, which is less efficient. And NNT is inherently related to efficacy because it derives from the observed treatment benefit (ARR) in a given context, not unrelated to efficacy.