Number needed to treat: Difference between revisions
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The '''number needed to treat''' is a way of summarizing the benefit of an intervention to improve health care.<ref name="pmid3374545">{{cite journal |author=Laupacis A, Sackett DL, Roberts RS |title=An assessment of clinically useful measures of the consequences of treatment |journal=N. Engl. J. Med. |volume=318 |issue=26 |pages=1728–33 |year=1988 |pmid=3374545 |doi=}}</ref> The calculations are derived from the results of a [[randomized controlled trial]] of an intervention. | The '''number needed to treat''' ('''NNT''') is a way of summarizing the benefit of an intervention to improve health care.<ref name="pmid3374545">{{cite journal |author=Laupacis A, Sackett DL, Roberts RS |title=An assessment of clinically useful measures of the consequences of treatment |journal=N. Engl. J. Med. |volume=318 |issue=26 |pages=1728–33 |year=1988 |pmid=3374545 |doi=}}</ref><ref name="pmid16174840">{{cite journal |author=Wen L, Badgett R, Cornell J |title=Number needed to treat: a descriptor for weighing therapeutic options |journal=Am J Health Syst Pharm |volume=62 |issue=19 |pages=2031–6 |year=2005 |pmid=16174840 |doi=10.2146/ajhp040558 |url=http://www.ajhp.org/cgi/pmidlookup?view=long&pmid=16174840}}</ref> The NNT has been proposed to improve [[quantitative literacy]].<ref name="pmid3374545"/> The calculations are derived from the results of a [[randomized controlled trial]] of an intervention. | ||
{| class="wikitable" align="center" | {| class="wikitable" align="center" | ||
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| Present || Absent|| | | Present || Absent|| | ||
|- | |- | ||
| rowspan="3"| | | rowspan="3"| || Experimental (intervention) group || Cell A|| Cell B||Total in experimental group | ||
|- | |- | ||
| Control group|| Cell C|| Cell D||Total in control group | | Control group|| Cell C|| Cell D||Total in control group | ||
| Line 26: | Line 26: | ||
:<math>\mbox{Number need to treat}=\left (\frac{100}{\mbox{Absolute risk reduction}}\right )</math> | :<math>\mbox{Number need to treat}=\left (\frac{100}{\mbox{Absolute risk reduction}}\right )</math> | ||
===Deriving the NNT from the odds or risk ratios=== | |||
The [[odds ratio]] may be used to derive the number needed to treat:<ref name="pmid11914297">{{cite journal |author=Furukawa TA, Guyatt GH, Griffith LE |title=Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses |journal=Int J Epidemiol |volume=31 |issue=1 |pages=72–6 |year=2002 |month=February |pmid=11914297 |doi= |url=http://ije.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11914297 |issn=}}</ref><ref name="pmid9139558">{{cite journal |author=McQuay HJ, Moore RA |title=Using numerical results from systematic reviews in clinical practice |journal=Ann. Intern. Med. |volume=126 |issue=9 |pages=712–20 |year=1997 |month=May |pmid=9139558 |doi= |url=http://www.annals.org/cgi/content/full/126/9/712 |issn=}}</ref> | |||
For odds ratios less than 1:<ref name="pmid9139558"/> | |||
:<math>NNT = \frac{1 - CER * (1 - OR)}{CER * (1 - OR)* (1 - CER)} \mbox{, where CER is control event rate and OR is odds ratio}</math> | |||
For odds ratios greater than 1:<ref name="pmid9139558"/> | |||
:<math>NNT = \frac{1 + CER * (OR - 1)}{CER * (OR - 1)* (1 - CER)} \mbox{, where CER is control event rate and OR is odds ratio}</math> | |||
The [[relative risk ratio]] may be used to derive the number needed to treat:<ref name="pmid11914297">{{cite journal |author=Furukawa TA, Guyatt GH, Griffith LE |title=Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses |journal=Int J Epidemiol |volume=31 |issue=1 |pages=72–6 |year=2002 |month=February |pmid=11914297 |doi= |url=http://ije.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11914297 |issn=}}</ref><ref name="pmid8601116">{{cite journal |author=Chatellier G, Zapletal E, Lemaitre D, Menard J, Degoulet P |title=The number needed to treat: a clinically useful nomogram in its proper context |journal=BMJ |volume=312 |issue=7028 |pages=426–9 |year=1996 |month=February |pmid=8601116 |pmc=2350093 |doi= |url=http://bmj.com/cgi/pmidlookup?view=long&pmid=8601116 |issn=}}</ref> | |||
:<math>NNT = \frac{1}{CER * (1-RRR)} \mbox{, where CER is control event rate and RRR is relative risk ratio}</math> | |||
The [[relative risk reduction]] may be used to derive the number needed to treat:<ref name="pmid11914297">{{cite journal |author=Furukawa TA, Guyatt GH, Griffith LE |title=Can we individualize the 'number needed to treat'? An empirical study of summary effect measures in meta-analyses |journal=Int J Epidemiol |volume=31 |issue=1 |pages=72–6 |year=2002 |month=February |pmid=11914297 |doi= |url=http://ije.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=11914297 |issn=}}</ref><ref name="pmid8601116">{{cite journal |author=Chatellier G, Zapletal E, Lemaitre D, Menard J, Degoulet P |title=The number needed to treat: a clinically useful nomogram in its proper context |journal=BMJ |volume=312 |issue=7028 |pages=426–9 |year=1996 |month=February |pmid=8601116 |pmc=2350093 |doi= |url=http://bmj.com/cgi/pmidlookup?view=long&pmid=8601116 |issn=}}</ref> | |||
:<math>NNT = \frac{1}{CER * (RRR)} \mbox{, where CER is control event rate and RRR is relative risk reduction}</math> | |||
==Example== | ==Example== | ||
==Variations== | |||
Years-needed-to-treat to add 1 year of life is proposed to estimate treatment effects.<ref name="pmid19164422">{{cite journal |author=Levy WC, Mozaffarian D, Linker DT, ''et al.'' |title=Years-needed-to-treat to add 1 year of life: a new metric to estimate treatment effects in randomized trials |journal=Eur. J. Heart Fail. |volume=11 |issue=3 |pages=256–63 |year=2009 |month=March |pmid=19164422 |doi=10.1093/eurjhf/hfn048 |url=http://eurjhf.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=19164422 |issn=}}</ref> | |||
==References== | ==References== | ||
| Line 34: | Line 52: | ||
==See also== | ==See also== | ||
[[Randomized controlled trial]] | * [[Randomized controlled trial]] | ||
* [[Absolute risk reduction]] | |||
* [[Relative risk reduction]] | |||
==External links== | |||
Tables of NNTs for various treatments: | |||
* [http://www.medicine.ox.ac.uk/bandolier/band50/b50-8.html Bandolier] | |||
* [http://www.cebm.utoronto.ca/glossary/nnts.htm#table University of Toronto Centre for Evidence-Based Medicine][[Category:Suggestion Bot Tag]] | |||
Latest revision as of 11:01, 27 September 2024
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.
See also
External links
Tables of NNTs for various treatments: