NNT, number needed to treat: Does it have any real value?

A. Pines*, S. Shapiro, S. Suissa

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review


Clinical trials usually use the relative risk (rate ratio or hazard ratio) to compare the effects of one treatment modality with others. However, the numbers needed to treat/harm (NNT/NNH) are sometimes used as another way of presenting an estimate of the effect of a medical intervention, pointing at the number of patients needed to be exposed over a certain period of time in order to achieve one beneficial or adverse event. For clinicians and patients, this is a very simple and clear tool to demonstrate the consequences of a specific intervention. Epidemiologists and statisticians are more cautious with interpretations of data of that sort. This article brings the relevant perspectives of a clinician, an epidemiologist and a statistician in regard to the value of NNT/NNH.

Original languageEnglish
Pages (from-to)139-142
Number of pages4
Issue number2
StatePublished - Apr 2012
Externally publishedYes


  • number needed to harm
  • number needed to treat


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