Number Needed to Treat


Health Economics

  • The number of patients needed to be treated with a particular therapy in order to prevent one additional bad outcome. The reciprocal of the absolute risk reduction (NNT = 1/ARR). Suppose an existing procedure entails a risk of an adverse effect of 0.005 while an alternative has a risk of 0.004, then ARR = 0.001 and NNT = 1000. Switching from the former to the latter procedure yields an expected reduction of one adverse event in every 1000 cases.
  • acronymNNT
    (written as number needed to treat)