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number needed to treat (NNT)

1/absolute risk reduction. For example, if mortality with treatment is 75% vs 90% for placebo, the absolute risk reduction is 0.90-0.75 = 0.15. Thus, the number need to treat is 1/0.15 = 6.667 ~ 7 The number of patients needed to treat for a single patient to benefit. If the prevalence in the population is low, the number needed to treat will be high.

Related

relative risk reduction (RRR)

General

statistics (biostatistics)

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 11, 14, 16, 17. American College of Physicians, Philadelphia 1998, 2006, 2012, 2015
  2. Cook RJ, Sackett DL. The number needed to treat: a clinically useful measure of treatment effect. BMJ. 1995 Feb 18;310(6977):452-4. PMID: 7873954 Free PMC Article
  3. Barratt A, Wyer PC, Hatala R et al Tips for learners of evidence-based medicine: 1. Relative risk reduction, absolute risk reduction and number needed to treat. CMAJ. 2004 Aug 17;171(4):353-8. Review. PMID: 15313996 Free PMC Article
  4. Saver JL, Lewis RJ. Number Needed to Treat. Conveying the Likelihood of a Therapeutic Effect, JAMA. Published online February 7, 2019 PMID: 30730545 https://jamanetwork.com/journals/jama/fullarticle/2724456
  5. Ranganathan P, Pramesh CS, Aggarwal R. Common pitfalls in statistical analysis: absolute risk reduction, relative risk reduction, and number needed to treat. Perspect Clin Res. 2016;7:51-3. PMID: 26952180
  6. The NNT: Quick summaries of evidence-based medicine. http://www.thennt.com/