Number needed to treat
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The number needed to treat (NNT) is a way of summarizing the benefit of an intervention to improve health care.[1][2] The NNT has been proposed to improve quantitative literacy.[1] The calculations are derived from the results of a randomized controlled trial of an intervention.
| Outcome | ||||
|---|---|---|---|---|
| Present | Absent | |||
| Experimental (intervention) group | Cell A | Cell B | Total in experimental group | |
| Control group | Cell C | Cell D | Total in control group | |
| Total with outcome | Total without outcome | |||
Calculations
Event rates
Measures of efficacy
Deriving the NNT from the odds or risk ratios
The odds ratio may be used to derive the number needed to treat:[3][4]
For odds ratios less than 1:[4]
For odds ratios greater than 1:[4]
The relative risk ratio may be used to derive the number needed to treat:[3][5]
The relative risk reduction may be used to derive the number needed to treat:[3][5]
Example
Variations
Years-needed-to-treat to add 1 year of life is proposed to estimate treatment effects.[6]
References
- ↑ 1.0 1.1 Laupacis A, Sackett DL, Roberts RS (1988). "An assessment of clinically useful measures of the consequences of treatment". N. Engl. J. Med. 318 (26): 1728–33. PMID 3374545. [e]
- ↑ Wen L, Badgett R, Cornell J (2005). "Number needed to treat: a descriptor for weighing therapeutic options". Am J Health Syst Pharm 62 (19): 2031–6. DOI:10.2146/ajhp040558. PMID 16174840. Research Blogging.
- ↑ 3.0 3.1 3.2 Furukawa TA, Guyatt GH, Griffith LE (February 2002). "Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses". Int J Epidemiol 31 (1): 72–6. PMID 11914297. [e]
- ↑ 4.0 4.1 4.2 McQuay HJ, Moore RA (May 1997). "Using numerical results from systematic reviews in clinical practice". Ann. Intern. Med. 126 (9): 712–20. PMID 9139558. [e]
- ↑ 5.0 5.1 Chatellier G, Zapletal E, Lemaitre D, Menard J, Degoulet P (February 1996). "The number needed to treat: a clinically useful nomogram in its proper context". BMJ 312 (7028): 426–9. PMID 8601116. PMC 2350093. [e]
- ↑ Levy WC, Mozaffarian D, Linker DT, et al. (March 2009). "Years-needed-to-treat to add 1 year of life: a new metric to estimate treatment effects in randomized trials". Eur. J. Heart Fail. 11 (3): 256–63. DOI:10.1093/eurjhf/hfn048. PMID 19164422. Research Blogging.